Answer:
A) The width is 12 cm; the average time is 3 minutes
Step-by-step explanation:

Cross multiply.
5 × y = 3 × 20
5y = 60
5y ÷ 5 = 60 ÷ 5
y = 12
The width is 12 cm. Moving onto the time.

Cross multiply.
4 × y = 12 × 1
4y = 12
4y ÷ 4 = 12 ÷ 4
y = 3
The time is 3 minutes.
A boy stands 1 meter away from a lamppost. He is 1.8 meters tall and casts a shadow 2 meters long in the light from the lamp
The diagram is attached below using the given information
We have two similar triangle
Triangle ACD is similar to triangle ABE. So the sides are in proportional

AC = AB + BC = 3m

2x = 1.8 * 3 (cross multiply)
2x = 5.4
Divide by 2 on both sides
x = 2.7
Height of Lamppost is 2.7 meter
Answer:
2.25, or 2 1/4.
Step-by-step explanation:
3/4 x 3 = 2.25
The product of the two is 0, so one of them have to equal 0 as any number multiplied by 0 is 0.
First solution: x - 4 = 0
If x - 4 = 0, then x = 4. So the first solution for <em>x </em>is 4.
Second Solution: -5x + 1 = 0
Solving...
-5x + 1 = 0
-5x = -1
x = -1/-5
x = 1/5 or 0.2
So x = 0.2 and 4