there are 37 terms in an AP the sum of 3 terms place exactly at the middle is 255 and the sum of the last three terms is 429 .write the AP
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Three middle terms will be = t18, t19, t20
Last three terms will be = t37, t36, t35
We know,
tn= a + (n-1)d
So,
t18 + t19 + t20 = 255
a + 17d + a + 18d + a + 19d = 255
3a + 54d = 255
a + 18d = 85. -: eqn 1
t37 + t36 + t35 = 429
after some calculations..
a + 35d = 143. :- eqn 2
Solve eqn 1 and eqn 2,and you will get the answer
Last three terms will be = t37, t36, t35
We know,
tn= a + (n-1)d
So,
t18 + t19 + t20 = 255
a + 17d + a + 18d + a + 19d = 255
3a + 54d = 255
a + 18d = 85. -: eqn 1
t37 + t36 + t35 = 429
after some calculations..
a + 35d = 143. :- eqn 2
Solve eqn 1 and eqn 2,and you will get the answer
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