Question

Amar wrote exams in four subjects-Physics, Chemistry, Biology and Social Studies. The ratio of marks he got in these exams was $2:3:4:5$. He got an aggregate of 70% in these exams. Each exam had the same maximum marks. In how many of these exams did he get more than 50%?

• A. $4$
• B. $1$
• C. $2$
• D. $3$

Answer 1

Answer: (D)

Let the maximum marks of each subject $=y$

Let the marks scored in Physics, Chemistry, Biology and social studies be $2x,3x,4x$ and $5x$.

Now, total marks scored in all 4 subjects $2x+3x+4x+5x=14x$

Total maximum marks of all 4 subjects $=4y$

Now according to question:

$(\frac{14x}{4y}\times 100)\%=70\%$

$\Rightarrow \frac{14x}{4y}\times 100=70$

$\Rightarrow y=5x$

$\%$ age of marks scored in Physics $=(\frac{2x}{5x}\times 100)\%=40\%$

$\%$ age of marks scored in Chemistry $=(\frac{3x}{5x}\times 100)\%=60\%$

$\%$ age of marks scored in Biology $=(\frac{4x}{5x}\times 100)\%=80\%$

$\%$ age of marks scored in Social Studies $=(\frac{5x}{5x}\times 100)\%=100\%$

So, he got more than $50\%$ in Chemistry, Biology and Social Studies.

Hence, the answer is $3$.