in an ap the first term is -5 and last term is 45.if the sum of all numbers in the ap is 120 then how many terms are there and what is the commom differnce
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YasminGautam:
and the other formula that i've written is used when last term is given.
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Answer:
Step-by-step explanation:
We have,
First term=a=(-5)
Last term= l=45
Then,
Sn= n/2( a+ l)
120= n/2(-5+45)
240= n(40)
n=6
No. Of terms=6
Common difference= d
120= 6/2(2×-5+5 d)
40=(-10) +5 d
d=50/5=10
Common difference=10
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