Question

what could be its answer

Answer 1

Let the first number of consecutive series be x

=> second number = x + 1
third number = x + 2

So the 15th number would be x + 14

Given, their average is 15

=> (x + x + 1 + ........ x + 14)/ 15 = 15

=> (x + x + 1 + ....... x + 14 ) = 225

Now,
There would be 15 x and the sum of constant term would be :-

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14

= 105

So,

(x + x + 1 + ........ x + 14) = 225

=> 15x + 105 = 225

=> 15x = 225 - 105

=> 15 x = 120

=> x = 120/15

=> x = 8


So first five numbers of this set would be

x + x + 1 + ...... x + 4

=> 8 + 9 + 10 + 11 + 12

Average =

(8 + 9 + 10 + 11 + 12)/5

=> 50/5

= 10

10 is your answer

Answer 2

Let 15 consecutive number be
=x,x+1,x+2,x+3,x+4,x+5,x+6,x+7,x+8,x+9,x+10,x+11,x+12,x+13,x+14,x+15.

(For your information consecutive numbers means number comes in series .Means if x=1
Then consecutive be X+1 means 1+1=2 hope you understand)
Back to question

Average=15

Average=sum of total numbers/total numbers
A/Q
$\frac{x + x + 1 + x + 2 + x + 3 + x + 4 + x + 5 + x + 6 + x + 7 + x + 8 + x + 9 + x + 10 + x + 11 + x + 12 + x + 13 + x + 14 }{15} = 15 \\ \frac{15x + 105}{15} = 15 \\ 15x + 105 = 15 \times 15 \\ 15x = 225 - 105 \\ x = 120 \div 15 \\ x = 8$
First five numbers
If x=8
Then consecutive numbers are
=8,9,10,11,12
By adding 1 on value of x
AVERAGe=8+9+10+11+12/5
=50/5
=10
AVERAGE=10

If not right report.
If right then thanks me