exponents

[grandh01]

1/2^10+1/2^11+1/2^12+1/2^12=?

1) 1/2^7
2) 1/2^8
3) 1/2^9
4) 1/2^13
5) 1/2^45

OA is C

[Anurag@Gurome]

1/2^10+1/2^11+1/2^12+1/2^12=?

1) 1/2^7
2) 1/2^8
3) 1/2^9
4) 1/2^13
5) 1/2^45

OA is C

1/2^10 + 1/2^11 + 1/2^12 + 1/2^12
= 1/2^10(1 + 1/2 + 1/2² + 1/2²)
= 1/2^10(1 + 1/2 + 1/4 + 1/4)
= 1/2^10(1 + 1/2 + 1/2)
= 1/2^10(1 + 1)
= 2/2^10
= [spoiler]1/2^9[/spoiler]

The correct answer is C.