Question
Before his last Physics test, Nitish's average for Physics was 33%. In his last test he scored 40% which increased his average to 34%. What must he score in his next test to increase his average to 35%?
Answer: Option D
:
D
Method 1: Equation Approach.
Suppose that Nitish wrote 'n' Physics tests before his last test.
Since his average is 33% in those n tests, the sum of his scores in those tests equal 33n percent.
He then scored 40% in his next test to increase his average to 34%.
The sum of all his scores is then equal to 33n+40 percent,giving an average of 33n+40n+1=34%. Solving this equation for n gives n=6.
Thus,if Nitish wants an average of 35 after 6+2 =8 tests,the sum of his scores should equal 8×35%=280%.
After 7 tests the sum of his scores equal 7×34%=238%,so he needs to score 280%−238%=42%in his eighth test.
Method 2: Alligation Approach
So, we can easily determine X=42%
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:
D
Method 1: Equation Approach.
Suppose that Nitish wrote 'n' Physics tests before his last test.
Since his average is 33% in those n tests, the sum of his scores in those tests equal 33n percent.
He then scored 40% in his next test to increase his average to 34%.
The sum of all his scores is then equal to 33n+40 percent,giving an average of 33n+40n+1=34%. Solving this equation for n gives n=6.
Thus,if Nitish wants an average of 35 after 6+2 =8 tests,the sum of his scores should equal 8×35%=280%.
After 7 tests the sum of his scores equal 7×34%=238%,so he needs to score 280%−238%=42%in his eighth test.
Method 2: Alligation Approach
So, we can easily determine X=42%
Was this answer helpful ?
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