0.99999999/1.0001 - 0.99999991/1.0003 =
A. 10^-8
B. 3(10^-8)
C. 3(10^-4)
D. 2(10^-4)
E. 10^-4
One approach is to recognize that both 9999.9999 and 9999.9991 can be rewritten as
differences of squares.
First,
0.99999999 = 1 - 0.00000001
=
(1 - 0.0001)(1 + 0.0001)
Similarly,
9999.9991 = 1 - 0.00000009
=
(1 - 0.0003)(1 + 0.0003)
Original question:
0.99999999/1.0001 -
0.99999991/1.0003
=
(1 - 0.0001)(1 + 0.0001)/(1.0001) -
(1 - 0.0003)(1 + 0.0003)/(1.0003)
=
(1 - 0.0001)(1.0001)/
(1.0001) -
(1 - 0.0003)(1.0003)/
(1.0003)
=
(1 - 0.0001) -
(1 - 0.0003)
= 1 - 0.0001 - 1 + 0.0003
= 0.0002
= 2 x 10^(-4) =
D
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
