In an AP the first term is-5 and last term is 45. If sum of all number in the AP is 120,. how many terms are there?what is the common difference?
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Answer:
Step-by-step explanation:
a = -5
a + (n-1)d = 45
Sn = n[a + an]/2
120 = n[40]/2
240 = 40n
n = 6
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