A disc Jokey must play 14 commercial spots during 1 hour of a radio show. Each commercial is either 30 or 60 seconds long. If the total commercial time during 1 hour is 11 min, how many 30 second commercials were played during that hour? How many 60 second commercials?

Question

Soybean mean is 16% protein; cornmeal is 8% protein. How many pounds of each should be mixed together in order to get 320-lb mixture that is 12% protein?

A student makes a $8.75 purchase at the bookstore with a $20 bill. The store has no bills and gives the change in quarters and fifty cent pieces. There are 30 coins in all. many quarters are there? How many fifty-cent pieces.

Answer 1

For the first problem

change 11 min to seconds by multiplying by 60. Because there is 60 seconds in one minute.

11 min. * (60 sec./1 min)
= 660 sec.

So for 30 sec. commercial
660/30 = 22 commercial

For 60 sec. commercial
660/60 = 11 commercial

Answer 2

Oops, forgot he wanted to play 14 commercials altogether.

If he did play only 30 sec. commercials he would be over 14.

For both 30 and 60 sec. commercials.

You would have to set up some sort of equation.

Answer 3

let the number of 30 sec commercials be x
then the number of 60 sec commericials is 14-x
11 min = 660 sec

solve : 30x + 60(14-x) = 660

(I get x=6, so 6 short commercials and 8 long ones)

Answer 4

for the second, solve for x

.16x + .08(320-x) = .12(320)
hint: multiply each term by 100 to get rid of decimals