Q. 174.8( 5 Votes )
Thesumsof an terms of two arithmetic progressions are in the ratio (7n – 5) : (5n + 17). Show that their 6th terms are equal.
Wrong question. It will be 7n + 5 instead of 7n – 5.
Given: Ratio of sum of n terms of 2 AP’s
To Prove: 6th terms of both AP’S are equal
Let us consider 2 AP series AP1 and AP2.
Putting n = 1, 2, 3… we get AP1 as 12,19,26… and AP2 as 22,27,32….
So, a1 = 12, d1 = 7 and a2 = 22, d2 = 5
S6 = 12 + (6 - 1)7 = 47
S6 = 22 + (6 - 1)5 = 47
Therefore their 6th terms are equal.
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