Average
- The average of 10 number is calculate as 15. It is discovered later on that while calculating the average one number , namely 36 was wrongly read as 26. The correct average is ?
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New sum of number = previous sum - 26 + 36
=10 x 15 - 26 + 36
= 160Correct Option: C
New sum of numbers = previous sum - 26 + 36
=10 x 15 - 26 + 36
= 160
∴ Correct Average = 160 / 10 = 16.
- The average of 13 result is 68. The average of first seven is 63 and that of the last seven is 70 , the seventh result is ?
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Seventh Result = sum of first 7 results + sum of last 7 results - sum of all 13 results.
Correct Option: A
Seventh Result = sum of first 7 results + sum of last 7 results - sum of all 13 results.
⇒ Seventh Result = (7 x 63) + (7 x 70) - (13 x 68 )
=47
- The average of 25 results is 18, that of first twelve is 14 and of last twelve is 17 . Thirteenth result is?
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Thirteenth Result = sum of all 25 results - sum of first 12 results - sum of last 12 results.
Correct Option: C
Thirteenth Result = sum of all 25 results - sum of first 12 results - sum of last 12 results.
= 25 x 18 - 12 x 14 – 12 x 17
=78
- The average temperature of Monday, Tuesday, Wednesday, and Thursday was 38° C and that of Tuesday, Wednesday, Thursday and Friday was 40° C, if the temperature on Monday was 30° C, the temperature of Friday was?
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Given
M + T + W + TH = 4 x 38° = 152°
T + W + TH + F = 4 x 40° = 160°
M = 30°
Correct Option: C
From question
M + T + W + TH = 4 x 38° = 152°
⇒ T + W + TH =152° – 30° = 122°
Again from question
⇒ T + W + TH + F = 4 x 40° = 160°
⇒ F = 160° – 122°
= 38°
- The average of 5 consecutive number is n , if the next two number are also include, the average of 7 number will ?
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Sum of 5 consecutive integers
x + ( x +1 ) + ( x +2 ) + ( x + 3 ) + ( x +4 ) = 5n
⇒ 5x + 10 = 5n
⇒ x = ( n – 2 ) ......(i)
Average of 7 consecutive integers
= [( 5x + 10 ) + ( x + 5 ) + ( x + 6 )] / 7
= 7x + 21 / 7
= x + 3 .....(ii)Correct Option: B
Sum of 5 consecutive integers
x + ( x +1 ) + ( x +2 ) + ( x + 3 ) + ( x +4 ) = 5n
⇒ 5x + 10 = 5n
⇒ x = ( n – 2 ) ......(i)
Average of 7 consecutive integers
= [( 5x + 10 ) + ( x + 5 ) + ( x + 6 )] / 7
= 7x + 21 / 7
= x + 3 .....(ii)
from eq. (i) and (ii)
New average = x + 3 = ( n – 2 + 3 ) = n + 1
So , the new average increases by 1 .