SOLUTION: 1. Tourists covered 640 km for a 4-hour ride by car and a 7-hour ride by train. What is the speed of the train, if it is 5 km PER HOUR greater than the speed of the car? 2. A mo

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Question 1027775: 1. Tourists covered 640 km for a 4-hour ride by car and a 7-hour ride by train. What is the speed of the train, if it is 5 km PER HOUR greater than the speed of the car?
2. A motorboat covers the distance from one pier to the other pier in 4 hours and the way back in 5 hours. What is the speed of the boat in still water, if it covers 70 km with the current in 3.5 hours?
3.Lilian has part of $9000 invested at 4% and the remainder at 6%. His annual return on each investment is the same. At what rate would she have to invest all her money to get the same interest?
4.Technological advances in farming made it possible to increase the crop of potatoes from 1 acre by 4 tons. As a result, from a field of 320 acres 640 tons of potatoes more were collected than before from a field of 400 acres. How many tons of potatoes were collected before the new methods and how many after the introduction of the new technology?
PLEASE HELP

Answer by josgarithmetic(39630)   (Show Source): You can put this solution on YOUR website!
Basic travel rates rule relates rate, time, distance, as RT=D.
                      RATE             TIME          DISTANCE

CAR                   r+5                4

TRAIN                 r                  7

Total                                                   640

Fill-in what's missing and solve.
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