In calvin’s chemistry class, her final grade consists of lab work and the final exam.

[BTGModeratorVI]

In Calvin’s chemistry class, her final grade consists of lab work and the final exam. If lab work is 2/3 of the final grade, and she scores 80%, what must she score on the final exam to earn a final grade of 75%?

A)65%
B)68%
C)70%
D)73%
E)75%

Answer: A
Source: GMAT Prep Now

[Brent@GMATPrepNow]

In Calvin’s chemistry class, her final grade consists of lab work and the final exam. If lab work is 2/3 of the final grade, and she scores 80%, what must she score on the final exam to earn a final grade of 75%?

A)65%
B)68%
C)70%
D)73%
E)75%

Answer: A
Source: GMAT Prep Now

Weighted average of groups combined = (group A proportion)(group A average) + (group B proportion)(group B average) + (group C proportion)(group C average) + ...

So, here we have: Final grade = (lab work weighting)(lab work grade) + (final exam weighting)(final exam grade)

Let x = final exam grade

Plug in values to get: 75 = (2/3)(80) + (1/3)(x)
Simplify: 75 = 160/3 + x/3
Multiply both sides by 3 to get: 225 = 160 + x
Solve: x = 65

Answer: A

Cheers,
Brent