Answer:
10.24 years
Step-by-step explanation:
The computation of the time period is as follows:
As we know that
Amount = Principal × (1 + rate of interest)^time period
£8000 = £4000 × (1 + 0.07)^time period
£8,000 ÷ £4,000 = 1.07^time period
2 = 1.07^time period
Now apply the log to the both sides
log 2 ÷ log 1.07 = time period
= 10.24 years
so 5 people work each one for 21 minutes, that means 21+21+21+21+21 minutes altogether, namely 105 minutes, it took that long for 7 walls, hmmmm how long for just one wall then? well, 105 ÷ 7, namely 15 minutes then, for just 1 wall.
now, if it takes 15 minutes of work to do one wall, what about 5 walls? well, that'd be 15*5 or 75 minutes.
so if we have 3 folks working, how much would each one work? well, 75 ÷ 3, namely 25 minutes, so each of them will work 25 minutes, namely 25+25+25 minutes, so in 25 minutes, they'll be done with 5 walls.
X + 5 + 11x = 12x + y
Simplify: 12x + 5 = 12x + y (We are adding x and 11x on the left side)
Subtract 12x from each side makes each zero.
5 = y
So we can plug in and test. I'm picking two random numbers to plug in for x. 10, and 82
x = 10, y = 5
10 + 5 + 11(10) = 12(10) + 5
125 = 125
x = 82, y = 5
82 + 5 + 11(82) = 12(82) + 5
989 = 989
So we verified y = 5
Well, for any prism, it is the lateral area + the area of two ends.
