5) Two high-speed ferries leave at the same time from a city to go to the same i

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%

Explanation / Answer

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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