Envelopes can be purchased for $1.50 per pack of 100, $1.00 per pack of 50, or $0.03 each. What is the greatest number of envelopes that can be purchased for $7.30?

(A) 426
(B) 430
(C) 443
(D) 460
(E) 486

The 3 options:
$1.50 per pack of 100 = 1.5 cents per envelope
$1.00 per pack of 50 = 2 cents per envelope
$0.03 per individual envelope = 3 cents per envelope

Since the packs of 100 are the best value, let's buy as many of these as we can.

4 packs of 100 costs $6.00 (we still have $1.30 left to spend)
1 packs of 50 costs $1.00 (we still have $0.30 left to spend)
10 individual envelopes costs $0.30 (we've spent all of the money)

Number of envelopes purchased = 400 + 50 + 10 = [spoiler]460 = D[/spoiler]

Cheers,
Brent