thanhnguyen
Which of the followings is closest to \(({{9^{102}}/{{3^4}}) - {3^4}\)?
A. \({({3^2})^{49}}\)
B. \(3^{100}.3^{100}\)
C. \(9^{99}\)
D. \(9^{50}\)
E. \(9^{48}\)
Dear
thanhnguyen,
I'm happy to help with this.
You may find this blog article relevant to this problem:
https://magoosh.com/gmat/2012/adding-and ... -the-gmat/\(({{9^{102}}/{{3^4}}) - {3^4} = ({{(3^2)^{102}}/{{3^4}}) - {3^4}\)
\(= ({{(3)^{204}}/{{3^4}}) - {3^4}\)
\(= (3)^{200} - {3^4}\)
At this point, \((3)^{200}\) is a truly gargantuan number, more than an Avogadro's number of Avogadro's numbers, more than the number of elementary particles in the Visible Universe. Meanwhile,
3^4 = 81 is a mere pittance by comparison, so this latter term doesn't matter at all. The entire thing is closest to \((3)^{200} = (9)^{100}\).
Now, neither form is listed as a choice, but choice
(B) has
B. \(3^{100}.3^{100}\)
The decimal point is not a recognizable mathematical operator, but if by this, the author intended multiplication, then the correct way to write this would be:
B. \((3^{100})*(3^{100})\)
By computer convention, the * sign (shift-8 on a QWERTY keyboard) is the proper symbol for multiplication. If this is what is intended by
(B), then
(B) is the correct answer.
Does all this make sense?
Mike