Help: Solution's wrong? Q6 of Math #1 in free practice test

[vivianqiu231]

Joe is twice as old as Ann. Eight years ago, Joe was four times older than Ann. Explanation:Eight years ago, Joe was four times older than Ann: J – 8 = 4(A – 8)

Is it wrong? Joe was four times older than Ann:
should be J-8=5(A-8)...Is my comprehension of the comparation wrong?

[tommywallach]

Four times translates literally as 4 * something. 5 * something would be five times.

You might be confusing the idea that if something is 400% of something else, you multiply the original by 4, but if it's said to have increased by 400%, you multiply the original by 5.

The cost of gasoline has increased by 400% over the past ten years.

Used to be x, now it's x + 4x = 5x.

The cost of gasoline is 400% of what it was ten years ago.

Used to be x, now it's 4x.

Hope that helps!

-t

[vivianqiu231]

Four times translates literally as 4 * something. 5 * something would be five times.

You might be confusing the idea that if something is 400% of something else, you multiply the original by 4, but if it's said to have increased by 400%, you multiply the original by 5.

The cost of gasoline has increased by 400% over the past ten years.

Used to be x, now it's x + 4x = 5x.

The cost of gasoline is 400% of what it was ten years ago.

Used to be x, now it's 4x.

Hope that helps!

-t

You are right, I understand.
From your point , the explanation of the math question is wrong,isn't it?
four times means 4*something, older means increase by , four times older than should be 5*age.
Four times the same age as or Four times as old as should be 4*age.
Anyway, thank you for your reply! Hope I haven't confused the times whatever.I will learn it further.

[tommywallach]

Hey Vivian,

No, this is correct. If I'm 4 times older than you, then you'd just multiply your age by 4 to get mine. Now if something "increases by 400%", you'd multiply it by 5. (Weird, I know.)

GOod luck!

-t