Expand the brackets:
5y + 50 = 40
minus 50 on both sides to get 5y alone
5y = -10
divide both sides by 5 to find y
y= -2
∴ 1/4y = -0.5
Answer: 56.4102564% decrease
Explanation: First determine whether the number is increasing or decreasing. Since it changes from 39 to 17, it's going down so it's decreasing.
Now to find the percent decrease,
we divide the amount of change by the original number.
The amount of change is the difference between the two numbers
which in this case is 39 - 17 and the original number is 39.

39 - 17 is 22 so we're left with
which gives us 56.4102564
Remember however that our problem is asking for a <em>percent</em>, not a decimal. So we need to write 56.4102564 as a percent by moving the decimal point 2 places to the right to get 56.4102564.
So when a number changes from 39 to 17, it has decreased by 56.4102564%.
Answer:
Surface area of cylinder = 50.26 unit² (Approx.)
Step-by-step explanation:
Given:
Radius of base r = 2 units
Width of lateral rectangle = 4 units
Length of lateral rectangle = 6.28 units
Find:
Surface area of cylinder
Computation:
Surface area of cylinder = 2[Area of base] + Area of lateral rectangle
Surface area of cylinder = 2[πr²] + [l][b]
Surface area of cylinder = 2[(22/7)(2)²] + [6.28][4]
Surface area of cylinder = 2[(22/7)(4)] + 25.12
Surface area of cylinder = 25.14 + 25.12
Surface area of cylinder = 50.26
Surface area of cylinder = 50.26 unit² (Approx.)