Let S = his average speed.
Let D = distance traveled one way
Time = distance / speed
Set up an equation:
d/6 + d/12 = 2d/S
Multiply the equation by 12s:
12s(d/6) + 12s(d/12) = 12s(2d/s)
Simplify to get:
2sd + sd = 24d
Combine like terms:
3sd = 24d
Divide both sides by d:
3s = 24
Divide both sides by 3:
s = 24/3
s = 8
His average speed was 8 mph.
Answer:
27
Step-by-step explanation:
Let the number to find out be 'x'
Therefore,
according to the condition given question, we get the equation as

Now,
squaring both the sides, we get
2x - 5 = 49
on adding 5 both sides, we get
2x - 5 + 5 = 49 + 5
or
2x = 54
or
x =
or
x = 27
Hence, the number is 27
Im not so sure about Q2 but 3 and 4 are correct for sure.
Answer: 390
Step-by-step explanation: