19. The average temperature of Monday, Tuesday, Wednesday and Thursday was $38^\circ $ and that of Tuesday, Wednesday, Thursday and Friday was $40^\circ $. If the temperature on Monday was $30^\circ $, the temperature of Friday was :
a. $40^\circ $
b. $39^\circ $
c. $38^\circ $
d. $30^\circ $
Answer: C
Explanation:
M + T + W + Th = $(4 \times 38) = 152$
Monday temparature is 30. So T + W + Th = (152 - 30) = 122
T + W + Th + F = $(4 \times 40) = 160$
F = (160 - 122) = $38^\circ $
20. A shop keeper earned Rs.504 in 12 days. His average income for the first four days was Rs.40 a day. His average income for the remaining days is :
a. Rs.40
b. Rs.42
c. Rs.43
d. Rs.45
Answer: C
Explanation:
Let the average for remaining 8 days be Rs.x a day. Then, $4 \times 40 + 8 \times x = 504$ or 8x = 344 or x = 43
Required average = Rs.43
21. A man whose bowling average is 12.4 takes 5 wickets for 26 runs and there by decreases his average by 0.4. The number of wickets taken by him before his last match is:
a. 85
b. 78
c. 72
d. 64
Answer: A
Explanation:
Let the number of wickets taken before the last match=x.
then $\displaystyle\frac{{12.4x + 26}}{{x + 5}} = 12 \Rightarrow x = 85$
22. The average of weight of three men A,B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg.more than that of D, replaces A, then the average weight of B,C,D and E becomes 79 kg. The weight of A is :
a. 70 kg
b. 72 kg
c. 75 kg
d. 80 kg
Answer: C
Explanation:
A + B + C = $3 \times 84 = 252$
A + B + C + D= $(4 \times 80) = 320$
D = (320 - 252)=68 and E = (68 + 3)=71
Now, B + C + D + E = $(4 \times 79) = 316$
B + C + D = (316 - 71) = 245 kg
So, A = (320 - 245) = 75 kg
23. The average age of A,B,C,D five years ago was 45 years. By including X, the present average age of all the five is 49 years. The present age of X is :
a. 64 years
b. 48 years
c. 45 years
d. 40 years
Answer: C
Explanation:
As 5 years ago average is 45, the present average is 50. So sum of the ages of A, B, C, D is 50 x 4 = 200
But given that average of A, B, C, D and X is 49. So sum of their ages = 49 x 5 = 245
Present age of X = 245 - 200 = 45 years.
24. The average age of 24 students in a class is 10. If the teacher's age is including, the average increases by one. The age of the teacher is :
a. 25 years
b. 30 years
c. 35 years
d. 40 years
Answer: C
Explanation:
Sum of the ten students age = 24 x 10
Sum of the ten students including the teacher = 25 x 11
Age of the teacher = $(25 \times 11 - 24 \times 10)$=35 years