Question : The average marks obtained by S1 and S2 is 30 more than the average marks obtained by S2 and S3. If the marks obtained by S3 is 50, then what are the marks obtained by S1?
Option 1: 80
Option 2: 105
Option 3: 95
Option 4: 110
Correct Answer: 110
Solution :
Given: The average marks obtained by S1 and S2 is 30 more than the average marks obtained by S2 and S3.
The mark obtained by S3 is 50.
Use the formula, $\text{Average}=\frac{\text{Sum of all values}}{\text{The total number of values}}$.
According to the question,
$\frac{\text{S1+S2}}{2}=\frac{\text{S2+50}}{2}+30$
⇒ $\frac{\text{S1+S2}}{2}–\frac{\text{S2+50}}{2}=30$
⇒ $\frac{\text{S1+S2–S2–50}}{2}=30$
⇒ $S1–50=60$
⇒ $S1=60+50=110$
Hence, the correct answer is 110.
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