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Which term of the AP 3,8,13,18,....,is 78? |
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Answer» Let a=3\xa0d = 5, (8-3)=5an = 7878 = a+(n-1)d78 = 3+ (n-1)578 = 3+5n-578 = -2 +5n78+2 = 5n80 = 5nn = 80/5n =\xa016 an=a+(n-1)d d= a2-a1 = 8-3 = 5if an =78 an=a+(n-1)d 78=3+(n-1)5 78=3+5n-5 78=-2+5n 80=5n therefore n=80÷5 16 |
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