Question

Sum of first hundred numbers common to the A.P's 12,15,18....and 17,21,25..... is

Answer 1

Answer:

61500

Step-by-step explanation:

The terms common to two AP's is also an AP with common difference D=LCM(d1,d2) and first term A= first term common to the two series

Since 21 is the 1st term common to these series

d1=3

d2=4

D=LCM(3,4)=12

Therefore the resultant AP has a=21 and d=12

Finding sum of 100 terms:

S=(100/2)[2(21)+(99)(12)]

S=100(21+594)

S=61500

Hope this answer helped you