In an A.Psum of its 15th and 28 th termsis 211 and difference of its42nd and 20 th termsis 110.then find sum of itsfirst 10 terms
Answers
Answered by
0
Answer:
285
Step-by-step explanation:
a42-a20=110
a+41d-[a+19d]=110
a+41d-a-19d=110
22d=110
d=110/22
d=5
a15+a28=211
a+14d+a+27d=211
2a+41d=211
2a+41[51]=211
2a+205=211
2a =211-205
2a=6
a=6
n=10
sn n/2 [2a+[n-1]d
s10=10/2[2*6+[10-1]5
5[12+[9]5]
5[12+45]
5*57
285
Similar questions