1.
The average age of 5 sons is 21 years. If the age of the youngest son be 5 years, find the average age of the family at the birth of the youngest son.
• A.
24 years
• C.
20 years
• B.
25 years
• D.
28 years
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Explanation :
Total age of 5 sons = 21 x 5 = 105 years
Total age of 4 sons at the birth of the younger son,
that is, 5 years ago = 105 – (5 x 5)
 = 80 years
Before the birth of the youngest son, the family consisted of only 4 sons.
Average age of 4 sons 5 years ago =
 80 4
= 20 years.
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2.
The daily maximum temperature for 7 consecutive days in May 1988 were 42.7°C, 44.6°C, 42.0°C, 39.1°C, 43.0°C, 42.5°C and 38.5°C. Find the average daily maximum temperature.
• A.
42.63°C
• C.
41.77°C
• B.
45.65°C
• D.
39.60°C
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Explanation :
Average daily maximum temperature =
 42.7 + 44.6 + 42.0 + 39.1 + 43.0 + 42.5 + 38.5 7

=
 292.4 7

 = 41.77°C
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3.
The average monthly expenditure of a family for the first four months is Rs 2750, for the next three months is Rs. 2940 and for the last five months Rs. 3130. If the family saves Rs. 5330 during the whole year, find the average monthly income of the family during the year.
• A.
Rs. 3800
• C.
Rs. 3400
• B.
Rs. 3500
• D.
Rs. 4200
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Explanation :
Average monthly expenditure of 4 months = Rs 2700
Total expenditure for 4 months = Rs 2700 x 4 = Rs. 11000
Average monthly expenditure of 3 months = Rs 2940
 Total expenditure of 3 months = Rs 2940 x 5 = Rs 8820 ….(i)
Average monthly expenditure of 5 months  = Rs 3130
 Total expenditure of 5 months = Rs 31020  = Rs 1560 ….(ii)
 Total expenditure in the whole year = Rs 11000 + 8820 + Rs. 15650
 = Rs. 35470.
Saving during the whole year = Rs. 5330
Total income of the family during the year = Rs. 35470 + Rs. 5330 = Rs. 40800
Average monthly income during the year =
 40800 12
= Rs. 3400
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4.
The average of 10 numbers is 7. What will be the new average if each of the numbers is multiplied by 8?
• A.
45
• C.
56
• B.
52
• D.
55
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Explanation :
The average of 10 numbers = 7
Total of 10 numbers = 10 x 7 = 70
New total of 10 numbers after each of given numbers is multiplied by 8 = 70 x 8 = 560
New average =
 560 10
= 56
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5.
There was one mess for 30 boarders in a certain hostel. On the number of boarders being increased by 10, the expenses of the mess were increased by Rs 40 per month while the average expenditure per head diminished by Rs 2, Find the original monthly expenses.
• A.
Rs. 390
• C.
Rs. 360
• B.
Rs. 410
• D.
Rs. 480