5(r - 10) = -51
= 5r - 50 = -51
= 5r = -51 + 50
= 5r = -1
= r = -1/5
r = -0.2
Answer:
143
Step-by-step explanation:
17 times 8 =136, 136 + 7 = 143
Answer:
-40
Step-by-step explanation:
If the current in a stream moves at a rate of 7 mph. If a boat travels 98 miles downstream in the same time that it takes to travel 49 miles upstream then the speed of the boat in still water is 21 miles per hour.
<h3>What is speed?</h3>
Speed is the distance covered by an object in a certain time period. It is also known as velocity. The formula of speed is as follows:
Speed=Distance/ Time.
<h3>How to calculate speed?</h3>
We have been given that the speed of stream is 7miles per hour.
Let v be the speed of the boat, and t the time to travel
98=t*(7+v) (1)
49=t(v-7) (2)
(1)+(2) => 2tv=147
7t+(49+7t)=98
14t+49=98
14t=49
t=49/14
t=7/2
Put the value of t in equation 1 to get the value of v:
98=t(7+v)
98=7/2(7+v)
196/7=7+v
28=7+v
v=28-7
v=21
Hence if the current in a stream moves at a rate of 7 mph. If a boat travels 98 miles downstream in the same time that it takes to travel 49 miles upstream then the speed of the boat in still water is 21 miles per hour.
Learn more about speed at brainly.com/question/4931057
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