Thread: Finding 'x' on an evenly spaced number line

This is from an SAT prep book:


Number 9 is what I have trouble with.
Please provide an explanation.
See attachment for problem.


The answer is not A. A was my guess.

Originally Posted by Masterthief1324

This is from an SAT prep book:


Number 9 is what I have trouble with.
Please provide an explanation.
See attachment for problem.


The answer is not A. A was my guess.

You need to travel five tick marks to get from 2 to 42. Each time you travel one tick mark you are adding a fixed value onto the previous tick mark's value.

For example, consider the simple number line:

| - | - | - |
1 - | - | - 4

Here, we travel 3 ticks from 1 to arrive at 4, so travelling three ticks increases our value by 3, so therefore travelling one tick increases our value by 1 (3/3 = 1)

Going back the number line in your question, we don't know exactly how much we add on with each tick travelled, but we do know that travelling 5 ticks from 2 adds on 40, since 2 + 40 = 42.

From this can you work out how much we add on when we travel one tick? When you have that value, you should be able to work out x, by travelling two ticks from 2.

Hope this helps.

You have a total of 40 spaces, now try to figure out where the x is at. You also have a break down of the 40 spaces.

Originally Posted by pomp

You need to travel five tick marks to get from 2 to 42. Each time you travel one tick mark you are adding a fixed value onto the previous tick mark's value.

For example, consider the simple number line:

| - | - | - |
1 - | - | - 4

Here, we travel 3 ticks from 1 to arrive at 4, so travelling three ticks increases our value by 3, so therefore travelling one tick increases our value by 1 (3/3 = 1)

Going back the number line in your question, we don't know exactly how much we add on with each tick travelled, but we do know that travelling 5 ticks from 2 adds on 40, since 2 + 40 = 42.

From this can you work out how much we add on when we travel one tick? When you have that value, you should be able to work out x, by travelling two ticks from 2.

Hope this helps.

What threw me off was the the phrase that prompted for the arithmetic sequence: 'equally spaced'

The answer is 18