Answer:
The speed on motorboat is 20 mph
Step-by-step explanation:
here, we want to find the speed on the motorboat
if he has a speed of x mph on the motor boat, his speed on the ski will be (x + 10) mph
The total hours is 4 hours
Mathematically; speed = distance/time
Time on ski is 27/x+ 10
Time on motor boat is 62/x
The addition of both is 4
Thus;
27/(x + 10) + 62/x = 4
27(x) + 62(x + 10) = 4(x)(x + 10)
27x + 62x + 620 = 4(x^2 + 10x)
89x + 620 = 4x^2 + 40x
4x^2 -49x-620 = 0
using the quadratic formula;
{-b ± √(b^2-4ac)}/2a
where a = 4, b = -49 and c = -620
= 49 ± √(-49)^2-4(4)(-620)/8
So we have
49+ 111/8 or 49-111/8
Speed cannot be negative
(49 + 111)/8
= 20 mph
60 miles per hour
so 156 miles = 156 /60 = 2.6 hours
0.6 x 60 = 36
so 2.6 hours = 2 hours 36 minutes
Kim leaves Rotherham at 7: 30AM
7:30 AM + 2 hours 36 minutes = 10:06 AM
Answer
Kim arrives in London after 10AM
One way of doing this would be to look at the πr² as if it were a single term. Then we could divide both sides by πr², which leaves h = V/πr².
Answer:
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