Question

plzz answer my question fast

Answer 1

Total number of logs =228
Number of logs in first row =30
Number of logs in second row =28
This is in arthematic progressions = a=30, a+d=28
Common difference =-2
An=a+(n-1)d
228=30+(n-1)-2
228=30+(n-1)-2
228-30=(n-1)-2
198=(n-1)-2
n-1=198/2
n-1=99
n=99+1n=100
Number of logs in last row =a+99×-2
=30-198
168

Answer 2

A.P:- 30,28,36,...
a=30
d=28-30 = -2
Sn=228

Sn= n/2[2a+(n-1)d]
228=n/2[2(30)+(n-1)-2]
456=n(60-2n+2)
456=n(62-2n)
456= -2n²+62n
2n²-62n+456=0
n²-31n+228=0
n²-19n-12n+228=0
n(n-19)-12(n-19)=0
(n-19)(n-12)=0
n=12 or n=19

No. of logs in the 12th row=a12
=a+(n-1)d
=30+(12-1)-2
=30-22
=8