Question

sum of the first n odd number is 625.what is the number n

Answer 1

Answer:

1st odd number is 1

the a.p is 1,3,5,7......n

an=a+(n-1)d

an=1+(n-1)2

=1+2n-2

=2n-1

sn=n÷2×a+an

625=n÷2×1+2n-1

625=n÷2×2n

2n2=625×2

n2=625×2÷2

n2=625

n=root of 625

n=25.

power and exponents are tough to type so understand the solution step by step easily.

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Answer 2

Answer:

n=25

Step-by-step explanation:

First n odd numbers

1,3,5.................2n-1

a=first term =1

n=number of terms =?

d= Common difference=2

last term =a+[n-1]d=1+[n-1]2=2n-1

Sum of n terms= (n/2)first term +last term)

=(n/2)(1+2n-1)

=n/2[2n]

=n2

Hence the n= 25.....

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