1:)
actually i still have doubt about how did u know from very beginning that each common term made an Ap i.e. they are at regular intervals?
Find sum of first hundred terms appearing in BOTH 17,21,25.........
and 16,21,26............
-
UP 0 DOWN 0 0 4
4 Answers
49a=21
d=20
n=100
and use sum of n terms for an AP wala formula! [1]
149both are AP...
Suppose one common term is a
the common difference for first is 4 and for second is 5
Next term in first ap = a+4
next term = a+8....a+12...a+16....a+20....a+24 and so on..
for second ap..
next terms= a+5...a+10...a+15...a+20...a+25
thus, a+20 is the next common term after a
thus for any common term a, the next common term will be a+20
for a+20, next common term will be (a+20)+20
thus as we can see an AP is being formed with common difference 20 and the first term by observation is 21! :)
hence the answer!
Hope I am clear enough!
Cheers.! :)