Zachary got $200 for his birthday. He bought a $50 stereo, 4 CDs at $9.99 each, and a 6-pack of root beer for $5.60. He put the rest in the bank. (Man, good taste in soda *and* he's saving for his future? Get him while he's single, ladies.) How much did Zachary put in the bank?

Answer

$200 - $50 - (4 x $9.99) - $5.60 = $104.44

To figure out the
total cost of 4 CDs at $9.99 each, we don't actually have to multiply
$9.99 by 4. That's too much work. Instead, we can round and then adjust
our figure later on to be more exact. Trust us—this will save you
valuable CD-buying time in the long run.

$9.99 is almost exactly
$10, so the CDs cost about $40 total. However, this estimate is $0.01
(one cent) too high for each CD. Since there are 4 CDs, the estimate is 4
cents too high. Instead of $40, the CDs cost $39.96. Well, golly gee,
that sounds a whole lot cheaper than $40! What marketing genius came up
with *that* idea? He should get a *raise*!