Question

Q. if the average of X+2,X+5,X+8,X+11 and X+14 is 20, then find the average of first three numbers?

options--A.15
--B.16
--C.17
--D.18



plz slove this step by step.​

Answer 1

Average=sum of observation/no. Of observation
20=x+2+x+5+x+8+x+11+x+14/5
20X5=5x+40
100-40=5x
60/5=x
12=x

Now we need to find the first three numbers and their average
1st number=12+2=14
2nd number=12+5=17
3rd number=12+8=20

So average =sum of observation/no. Of observation
Average =14+17+20/3=51/3=17
So option C is correct