SCSA Mathematics Methods The logarithmic function
15 sample questions with marking guides and sample answers · Avg. score: 63.1%
Solve for in the following.
Reveal Answer
Changing from log to index form
| Descriptor | Marks |
|---|---|
correctly establishes the linear equation | 1 |
determines x | 1 |
Reveal Answer
Using addition log law
Equating and rearranging
Factorising
| Descriptor | Marks |
|---|---|
correctly applies the log law | 1 |
establishes quadratic equation | 1 |
determines 2 solutions | 1 |
Consider the function . The function is a vertical translation of by units.
Express the function in terms of a vertical translation of (i.e. in the form ), stating the number of units that is translated.
Reveal Answer
is translated vertically (upward) by units.
| Descriptor | Marks |
|---|---|
expresses as a sum of logs | 1 |
recognises a vertical translation by units | 1 |
The function is a vertical dilation of by a scale factor of .
Express the function in terms of a vertical dilation of , stating the scale factor.
Reveal Answer
is scaled vertically by a factor of 0.5.
| Descriptor | Marks |
|---|---|
expresses as a product involving | 1 |
recognises a vertical scaling by a scale factor of 0.5 | 1 |
The function is a horizontal dilation of by a scale factor of .
Express the function in terms of a horizontal dilation of , stating the scale factor.
Reveal Answer
is scaled horizontally by a scale factor of .
| Descriptor | Marks |
|---|---|
expresses 4 as | 1 |
expresses using a single logarithm | 1 |
states horizontal scale factor | 1 |
Solve for .
Reveal Answer
where
or
or
| Descriptor | Marks |
|---|---|
Forms a quadratic equation in terms of (e.g., ) | 1 |
Solves the quadratic equation to find and | 1 |
States the correct final answer , correctly discarding the invalid solution | 1 |
The pH of a substance is a measure of its acidity and is given by the formula where is the concentration of hydrogen ions in moles per litre. If a solution has a pH equal to 0.2, the concentration of hydrogen ions in moles per litre is closest to
0.32
0.63
0.70
1.58
Reveal Answer
0.32
This value is incorrect. It is close to rather than the required .
0.63
Rearranging the formula gives . Substituting the given pH, .
0.70
This value is incorrect and does not result from solving the logarithmic equation for .
1.58
This result comes from calculating , which incorrectly ignores the negative sign in the pH formula.
The graphs of the functions and intersect at point A. Determine the coordinates of point A.
(1.609, 15)
(1.099, 1)
(0.4065, 2)
(-0.693, 6)
Reveal Answer
(1.609, 15)
Incorrect. While this point lies on the graph of (since gives ), . The intersection point must satisfy both equations.
(1.099, 1)
Incorrect. This point lies on the graph of (since gives ), but . The functions are not equal at this x-value.
(0.4065, 2)
Incorrect. This point lies on the graph of (since gives ), but . The y-values differ significantly.
(-0.693, 6)
Correct. Set and multiply by to get the quadratic . Factoring gives . Since , , which yields and .
Solve for .
Reveal Answer
| Descriptor | Marks |
|---|---|
Expresses as and equates the exponents, e.g., | 1 |
Solves for to find the correct answer, | 1 |
Find the maximal domain of , where .
Reveal Answer
Maximal domain when
From NFL and
| Descriptor | Marks |
|---|---|
Identifies that the argument of the logarithm must be strictly positive, | 1 |
Factorises the quadratic expression or finds the critical values, e.g., | 1 |
States the correct maximal domain using union notation, | 1 |
Solve the following equations.
Reveal Answer
| Descriptor | Marks |
|---|---|
correctly determines | 1 |
Reveal Answer
Using log laws
Change from log to index form
| Descriptor | Marks |
|---|---|
correctly establishes equation using log laws | 1 |
correctly establishes the quadratic equation | 1 |
determines x | 1 |
A football coach offered a 12-day intensive training clinic. During the clinic, the height that each player could kick a football was monitored.
One player's kick heights could be modelled by , , where is vertical height (m) and is the time (days) spent in training.
Determine the initial height that the player could kick the ball.
Reveal Answer
| Descriptor | Marks |
|---|---|
Correctly determines the initial height | 1 |
Determine the training time needed for the player to be able to kick the ball to a height of 7 m.
Reveal Answer
Using a GDC:
| Descriptor | Marks |
|---|---|
Correctly determines the time required | 1 |
Determine the overall improvement in kick height achieved by completing the clinic.
Reveal Answer
Initially, the kick height was 6 metres.
At the end of the course, , the kick height increased
to 7.1139 metres.
The kick height has increased by 1.1139 metres during the
course.
| Descriptor | Marks |
|---|---|
Correctly determines the kick height at the end of the course | 1 |
Determines the overall kick height improvement | 1 |
Determine the rate of change in kick height when days.
Reveal Answer
Using a GDC:
| Descriptor | Marks |
|---|---|
Correctly determines the derivative value when | 1 |
Determine the training time (as a decimal) when the rate of change in kick height is 0.09 m/day.
Reveal Answer
Using a GDC:
Graph derivative function and
Find point of intersection.
| Descriptor | Marks |
|---|---|
Correctly determines the time as a decimal | 1 |
is equivalent to
0
1
Reveal Answer
0
This is incorrect. The expression evaluates to , not the constant 0. Furthermore, is undefined at .
1
This is incorrect. The expression would only equal 1 if (since and ), but it is not equal to 1 for all values of .
This is correct. The natural logarithm function and the exponential function are inverse functions, so for all .
This is incorrect. This result corresponds to , not the original expression.
A horizontal point of inflection is a point of inflection that is also a stationary point.
Determine the value/s of for which the graph of has only one horizontal point of inflection.
Reveal Answer
Stationary points
(i)
The quadratic has real roots when discriminant
There is only ONE phi
(not valid)
and so
Sub into (i) to determine the x-ordinate of the stationary point.
For
For
For each value, is the x-ordinate of both a stationary point () and a point of inflection ()
There is a point of horizontal inflection at when
| Descriptor | Marks |
|---|---|
correctly determines the first derivative | 1 |
correctly determines the quadratic equation to identify the stationary point/s | 1 |
determines valid and non-valid solutions of k | 1 |
determines x-ordinate of stationary point | 1 |
determines values of second derivative for both values of k | 1 |
shows logical organisation communicating key steps | 1 |
Determine .
Reveal Answer
This answer is incorrect. It corresponds to evaluating an antiderivative like only at the upper limit , neglecting to subtract the value at the lower limit.
This is incorrect. The evaluation of the definite integral depends on the limits and , which results in , not .
This option is incorrect. It may result from an arithmetic error or misapplying logarithmic properties, as the integral yields , not .
We factor out the constant to get . The antiderivative is , which simplifies to since .
The number of koalas in a conservation park is modelled by , , where represents the time (years) since the park opened. There were 20 koalas in the park when it opened.
Determine the approximate rate of change in the number of koalas when .
46
26
25
5
Reveal Answer
46
This is the value of the function . This represents the number of koalas (or the population increase) at year 3, rather than the rate at which the population is changing.
26
This value appears to be the result of calculating . This subtracts the initial population from the model's value at , which does not represent the instantaneous rate of change.
25
This is an incorrect value. It does not correspond to the derivative at or the function value, likely resulting from a calculation error.
5
The rate of change is found by taking the derivative . Using the chain rule, . Evaluating at gives , which rounds to 5.
A marble moves in one direction in a straight line with velocity (in metres per second) where is time (in seconds) since the marble passed through the origin.
Determine the distance from the origin the marble has rolled after 4 seconds.
0.40 m
1.60 m
3.22 m
8.09 m
Reveal Answer
0.40 m
This value represents the acceleration at , found by differentiating the velocity function: .
1.60 m
This value corresponds to , which is an intermediate value in the calculation but not the final integral result.
3.22 m
This is the instantaneous velocity of the marble at , calculated as , rather than the total distance traveled.
8.09 m
Distance is found by integrating velocity from to : .
Given that , the values of for which is a positive integer are
,
,
,
,
,
Reveal Answer
,
If , then , which does not result in an integer value for .
,
Converting the logarithmic equation to exponential form gives . Substituting with a positive integer yields .
,
If , then , which does not evaluate to an integer for positive integers .
,
If , then , which is only an integer when itself is a power of 2, not for all positive integers .
,
If , then , which does not yield an integer for positive integers .
Given that , determine the value of
77.800
10.778
2.778
1.556
Reveal Answer
77.800
This result comes from incorrectly multiplying the given logarithm by 100 (). However, , which involves addition, not multiplication.
10.778
This option incorrectly adds 10 to the given value. Since , you must add the exponent 2 (because ), not the base 10.
2.778
Using the product rule for logarithms, . Substituting the values gives .
1.556
This value represents , which equals . The logarithm of a product () requires adding the logs, not multiplying the log value by 2.