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# Solving Applied Problems: Two Equations?

Solve.

1.) Radio Airplay. Rudy must play 12 commercials during his 1-hr radio show. Each commercial is either 30 seconds or 60 seconds long. If the total commercial time during the hour is 10 minutes, how many commercials of each type does Rudy play?

2.) Etch Clean Graphics uses one cleanser that is 25% acid and a second that is 50% acid. How many liters of each should be mixed to get 10 L of a solution that is 40% acid?

3.) Darren paddled for 4 hr with a 6-km/h current to reach a campsite. The return trip against the same current took 10 hr. Find the speed of Darren's canoe in still water.

### 1 Answer

- ranjankarLv 77 years agoFavorite Answer
Let the no of " 60 seconds " commercial be x

Then the no of "30 seconds " commercial will be 12 - x

Total commercial time = 60x + 30 (12-x) = 10*60

60x +360 - 30x = 600

30x = 240

x = 8

ANSWER 8 commercials ( 60 seconds) AND 4 commercials ( 30 seconds)

CHECK

8X 60 = 480

4X 30 = 120

ADD = 600 seconds = 10 minutes

2) Let the quantity of 50% acid mixed be x liters

Then the quantity of 25% acid mixed will be (10 - x) liters

0.50x + 0.25 ( 10-x) = 0.40*10

0.50x + 2.50 - 0.25x = 4

0.25x = 1.50

x = 6

ANSWER 6 liters (50%) and 4 liters (25%)

CHECK

0.50 X 6 = 3

0.25 X 4 = 1

ADD 4

4/10 X 100 = 40%

3) Let the speed of Darren's canoe in still water be x km/ hour

Speed of current = 6km/ hour

DOWNSTREAM

-------------------------

Speed = ( x+6) km/ hour

Distance traveled = Speed X time

= ( x+6) X 4 = 4x +24 km

UPSTREAM

----------------

Speed = ( x-6) km/ hour

Distance = 10 ( x-6) = 10x -60 km

DISTANCE TRAVELED EACH WAY IS SAME

10x - 60 = 4x + 24

6x = 84

x = 14

ANSWER 14km/ hour

CHECK

4 ( 14+6) = 80km

10 ( 14-6) = 80km

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