Q7 of 110 Page 48

The fifth term of a G.P. is 1875. If the first term is 3, find the common ratio.

a1 = 3 and a5 = 1875

∵ an = a1rn-1 (n = no. of term, a1 = first term of G.P, r = common ratio)


⇒ a5 = a1r4


⇒1875 = 3r4 ………(1)



⇒ r5 = 625


⇒ r5 = 55


⇒ r = 5 is the common ratio.


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