Average Practice Test 1

Question : 36 of 40

Marks: +1, -0

The weight of a body, calculated as the average of seven different experiments is 53.735 grams. The average of the first three is 54.005 grams, the fourth was greater than the fifth by 0.004 gram, while the average of the sixth and seventh was 0.010 gram less than the average of the first three. What is the weight of the body as obtained by the fourth experiment?

53.068 gm
53.078 gm
53.086 gm
53.072 gm

Validate

Solution:

Total weight of 7 experiments = 53.735 × 7 = 376.145 gm
Total weight of first three = 54.005 × 3 = 162.015 gm
The average of the 6th and 7th was 0.010 gm less than that of the first three.
∴ Average of the 6th and 7th = 54.005 – 0.010 = 53.995 gm
∴ Total of the 6th and 7th = 53.995 × 2 = 107.990 gm
Thus, total of 4th and 5th = 376.145 – (162.015 + 107.990) = 106.140 gm
The fourth was greater than the fifth by 0.004 gm
∴ The fifth

= (106.140 - 0.004)× 1/2

=106.136/2 = 53.068

gm
Hence, the fourth = 53.068 + 0.004 = 53.072 gm

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