Question

5) Two​ high-speed ferries leave at the same time from a city to go to the same island. The first​ ferry, the​ Cat, travels at

36 miles per hour. The second​ ferry, the​ Bird, travels at 23 miles per hour. In how many hours will the two ferries be 26 miles​ apart?

The ferries will be 26 miles apart after ...hour(s).

6) Jane took 30 min to drive her boat upstream to​ water-ski at her favorite spot. Coming back later in the​ day, at the same boat​ speed, took her

15 min. If the current in that part of the river is 4km per​ hr, what was her boat speed in still​ water?

Her boat speed in still water was.......km per hr.

7) How many quarts of pure antifreeze must be added to 7 quarts of a 40​% antifreeze solution to obtain a 50​% antifreeze​ solution?

... ​quart(s) of pure antifreeze must be added.

8) How much water should be added to 10mL of 14​% alcohol solution to reduce the concentration to 5​%?

We should add...mL.

9) In planning her​ retirement, Liza deposits some money at 3.5% ​interest, with twice as much deposited at 5%. Find the amount deposited at each rate if the total annual interest income is $2430. She deposited ​$... at 3.5% and $...at 5%

Answer 1

5. Let time taken to make distance b/w 2 ferries be x hr. Then,

We know that, speed* time = distance

23x + 26 = 36x

=> x= 26/13

=> x =2 Km

6. upstream time = 30 min

downstream time = 15 min

The speed of river = 4 Km/hr

Let the speed of the boat in still water = v

Distance = speed * time

So, (4+v)*15 = (v-4)*30

=> 4+ v =2v -8

=> v = 12

=> v = 12 Km/hr

7. Let x quarts of pure antifreeze need to be added .

Then

7*0.4 + x = (7+x)*0.5

=> 2.8 + x = 3.5 + 0.5x

=> 0.5x= 0.7

=> x = 1.4 quarts

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