GMAT Prep - PS Ratio & Proportion

[albertrahul]

I'm not sure I understand GMAT answer here, please help me understand that.

My solution:
Let History Majors = 10

English Majors (Twice of History) = 20

Maths Majors (Three times of English) 20*3 = 60

So ratio of History to maths = 10:60 = 1:6

What is incorrect here, please explain.
My answer is ofcourse incorrect

[microke]

Let history majors =x
so,English majors =2x -Eqn(1)

Let maths majors =y
So english majors =3y -Eqn (2)

Using equations (1) and (2) y=2x/3

History: Maths = x:y =x: 2x/3 i.e. 3:2

The right answer is 3 to 2

[beeparoo]

I'm not sure I understand GMAT answer here, please help me understand that.

My solution:
Let History Majors = 10

English Majors (Twice of History) = 20

Maths Majors (Three times of English) 20*3 = 60 <--This is where you screwed up. "Eng majors are 3 times as many as Math majors", which means that E = 3*M or M = 20/3.

So ratio of History to maths = 10:60 = 1:6

What is incorrect here, please explain.
My answer is ofcourse incorrect Now you know why. Turn that frown upside-down!

~Sandra

[albertrahul]

Thank you both
I shall read questions more carefully.

[ksh]

Let history majors =x
so,English majors =2x -Eqn(1)

Let maths majors =y
So english majors =3y -Eqn (2)

Using equations (1) and (2) y=2x/3

History: Maths = x:y =x: 2x/3 i.e. 3:2

The right answer is 3 to 2

Hi microke,
I think your answer is reversed

HM=2EM
MM=3EM

So, HM/MM=2/3

am i wrong?

[albertrahul]

OA is B

[microke]

ksh:

A ratio in general should not involve fractions. For example, 1:1/3, though it not incorrect to express like this, it always mathematically correct to represent any ratio in integers:

1:1/3 is written as 3:1....by multiplying three on both sides of the fraction....hope it clarifies your doubt....