Question

If y=8 when x =3, find y when x=45

Answer 1

We have an equation: 3/8= 45/? (= x/y)

Cross multiply:
3*?= 8*45
⇒ ?= 8*45/3= 120

Final answer: y= 120~

Answer 2

Let's make things easier by simplifying things.

y = 8 and x = 3 is more likely to be understood as a ratio. So for the rest of the answer, their relationship would be represented as y:x

Thus: y:x = 8:3

The problem would be finding y when x = 45

Let us proceed on using the previous equation and substitute x with 45 which would look like this:

y:45 = 8:3

Ratios can also be expressed as fractions which would make things more understandable and easy to solve. So the new form of our equation would be like this:

y/45 = 8/3

Then we proceed with a cross multiplication where the equation becomes like as what is shown below:

3y = 45 * 8

From there, you can solve it by multiplying 45 and 8 then dividing the product with 3 to get y

3y = 360

y = 120

Another way of looking at the problem, especially problems like these, is to take the whole question or statement as an equation. it would probably look like this:

y = 8 when x = 3 : y = ? when x = 45

This would make you understand what approach you can use to solve the given problem.