25. The average of marks obtained by 120 candidates was 35. If the average of marks of passed candidates was 39 and that of failed candidates was 15, the number of candidates who passed the examination is :
a. 100
b. 110
c. 120
d. 150
Answer: A
Explanation:
Let the number of candidaes who passed =x, Then,
$39 \times x + 15\times (120 - x) = 120 \times 35$
24x = 4200-1800 or
x = $\left( {\displaystyle\frac{{2400}}{{24}}} \right) = 100$
26. The average expenditure of a man for the first five months is Rs.120 and for the next seven months it is Rs.130. If he saves Rs.290 in that year, his monthly average income is :
a. Rs.140
b. Rs.150
c. Rs.160
d. Rs.170
Answer: B
Explanation:
Total income = Rs.$(120 \times 5 + 130 \times 7 + 290) $=Rs.1800
Average monthly income
= Rs. $\left( {\displaystyle\frac{{1800}}{{12}}} \right)$=Rs.150
27. The average salary of 20 workers in an office is Rs.1900 per month. If the manager's salary is added, the average salary becomes Rs.2000 p.m. What is the manager's annual salary?
a. Rs.24,000
b. Rs.25,200
c. Rs.45,600
d. None of these
28. The average weight of a class of 40 students is 40 kg. If the weight of the teacher is included, the average weight increases by 500 gms. The weight of the teacher is :
a. 40.5 kg
b. 60 kg
c. 60.5 kg
d. 62 kg
Answer: C
Explanation:
Weight of the teacher =$(41 \times 40.5 - 40 \times 40)$kg=60.5 kg
29. The average weight of 8 men is increased by 2 kg when one of the men, whose weight is 50 kg is replaced by a new man. The weight of the new man is :
a. 52 kg
b. 58 kg
c. 66 kg
d. 68 kg
Answer: C
Explanation:
Weight increased = $(8 \times 2)$ kg = 16 kg
Weight of new man = (50+16)kg = 66 kg
30. The average weight of 8 persons is increased by 2.5 kg, When one of them whose weight is 56 kg is replaced by a new man. The weight of the new man is :
a. 66 kg
b. 75 kg
c. 76 kg
d. 86 kg
Answer: C
Explanation:
Total increase = $(8 \times 2.5)$ kg=20 kg.
Weight of new man = (50+16)kg=66 kg