Let's eight sequentially number are x, x + 1, x + 2, x + 3, x + 4, x + 5, x + 6 and x + 7.
According to the question [(x + 3) + (x + 4)]/2 = 6

Correct Option: B

Let's eight sequentially number are x, x + 1, x + 2, x + 3, x + 4, x + 5, x + 6 and x + 7.
According to the question [(x + 3) + (x + 4)]/2 = 6
⇒ (2x + 7)/2 = 6 ⇒ 2x + 7 = 12
⇒ 2x = 5 ⇒ x = 5/2

∴ Sum of all eight numbers = x + x + 1 + x + 2 + x + 3 + x + 4 + x + 5 + x + 6 + x + 7
= 8x + 28
= 20 + 28
= 48

Average of consecutive numbers = (first number + last number)/ 2

Correct Option: D

Let the four consecutive even number are x, ( x+2), (x+4), (x+6).
Clearly this is a series of consecutive even numbers
According to the formula,
Average of consecutive numbers = (first number + last number)/ 2
⇒ 27 = [x + (x + 6)]/2
⇒ x + 3 = 27
∴ x =24

∴ Greatest number = 4th consecutive even number = (x + 6) = 24 + 6 = 30

Total cost of 30 TV sets = ₹ 300000
Total cost of 15 TV sets = 9000 x 15 = 135000
Total cost of remaining 15 TV sets = 300000 - 135000 = 165000

Correct Option: C

Total cost of 30 TV sets = ₹ 300000
Total cost of 15 TV sets = 9000 x 15 = 135000
Total cost of remaining 15 TV sets = 300000 - 135000 = 165000

∴ Average cost of remaining TV sets = 165000/15 = ₹ 11000

Total age of 30 girls = 30 x 13 = 390 yr
Total age of 18 girls = 18 x 15 = 270 yr.
∴ Age of remaining 12 girls = 390 - 270 = 120 yr

Correct Option: B

Total age of 30 girls = 30 x 13 = 390 yr
Total age of 18 girls = 18 x 15 = 270 yr.
∴ Age of remaining 12 girls = 390 - 270 = 120 yr
∴ Required average = 120/12 = 10 yr

Let the numbers A, B, C, and D are N , N+1, N + 2 and N + 3, respectively.
According to the question,
[N + (N+1) + (N+2) + (N+3)] / 4 = 49.5

The required product = B x D
= (N + 1) x (N + 3)

Correct Option: A

Let the numbers A, B, C, and D are N , N+1, N + 2 and N + 3, respectively.
According to the question,
[N + (N+1) + (N+2) + (N+3)] / 4 = 49.5
⇒ 4N + 6 = 4 x 49.5
⇒ 4N = 198 - 6 ⇒ N = 192/4
⇒ N = 48

The required product = B x D
= (N + 1) x (N + 3)
= (48 +1) (48 +3 )
= 49 x 51
= 2499