Answer: 15

Explanation:
The present average age is (x + 3) when the old member is present and it equals to x when an old member is replaced by a new one.
The difference in the ages of the old member and the new one is equal to the difference in the total age before and after the replacement = 15 years.

Answer: 19

Explanation:
Average of 20 numbers = 0.
Sum of 20 numbers (0 x 20) = 0.
It is quite possible that 19 of these numbers may be positive and if their sum is a then 20th number is (-a).

Answer: Rs. 7.98

Explanation:

Answer: 179

Explanation:
Total runs scored by the batsman = 60*46 = 2760 runs
Now excluding the two innings the runs scored = 58*44 = 2552 runs
Hence the runs scored in the two innings = 2760 – 2552 = 208 runs.
Let the highest score be x, hence the lowest score = x – 150
x + (x - 150) = 208
2x = 358
x = 179 runs

Answer: 25

Explanation:
Sum of 8 results = 8(20) =160
Sum of first two results = 2(15.5) = 31
Sum of next three results = 3(21 1/3) = 64
The sixth result be x, Seventh result = x+4 Eighth result = x+7
31 + 64 + x + x + 4 + x + 7 = 160
X = 18, so last result = 18+7 =25

Answer: 52.5

Explanation:
Total marks secured by 36 students = 52 × 36 = 1872
Total marks secured by 36 students(Corrected) =1872-46+64 = 1890
∴Correct Average = 1890 / 36 = 52.5
Alternatively, Increase in the total marks when the error is corrected = 64-46 = 18.
The average of 32 students will increase by 18/36 = 0.5.
Hence the corrected average = 52 + 0.5 = 52.5

Answer: 30

Explanation:
Average age of X1 = ∑X_men / 8 (1)
= ∑X_men = 8X1
Let ages of two women be A, B
∑X _new = ∑X _men – (20 +24) + (A + B)
X1 + 2 = (= ∑X _men – 44 + (A + B)) / 8
Equations (1) and (2) gives:
44/8 – (A + B)/8 = -2
44 – (A +B) = -16
A + B = 60
Average age of women = 60/2 = 30 years

Answer: Rs. 500

Explanation:
The total cost of 30 horses = Rs. 12000.
The cost of the 12 horses = Average cost of 12 horses × 12 =250 ×12= 3000.
The cost of the remaining 18 horses, = 9000 / (30 – 12) = 9000 / 18 = Rs. 500

Answer: 645

Explanation:
Let the number of workers be x
85x + 525(15) = 95(x + 15) =>x = 645

Answer: 39

Explanation:
Had the batsman scored 15 runs in the last inning, his average would have been constant at 15. He scores 8 runs more than 15, which raises his average by 1.
∴ The last must have been his 8 / 1 = 8th innings.
To raise his average by 3, he required to score 8 × 3 = 24 runs more than his previous average in the 8th innings => he need to score 39