Question

answer these percent questions.
you are given the old amount and the percent of change.
find the new amount.
for problems 5 and 6, fill in the bubble for the correct answer.

1. what is $125 increased by 20%?
2. what is 42 increased by.08%?
3. what is $5,680 decreased by \frac{1}{2}\\%?
4. what is $452 increased by 5\frac{1}{4}\\%?
5. meis electric bill is $65 a month.

she read that she can reduce her electric bill by 15% each month if she changes to compact fluorescent light (cfl) bulbs.
she changes all of her bulbs to cfls.
how much should she expect her electric bill to be next month?
a. $55
b. $9.75
c. $76.47
d. $55.25
e. $50

1. as part of his city taxes each year, rohan has to pay a trash pickup fee of $42.

next year the fee is increasing by 110%.
how much will the fee be next year?
a. $462
b. $60
c. $20
d. $46.20
e. $88.20

Explanation:

Step1: Calculate the new amount for each problem

For percentage increase: \(New\ amount=Old\ amount\times(1 + \frac{Percent\ of\ change}{100})\)
For percentage decrease: \(New\ amount=Old\ amount\times(1-\frac{Percent\ of\ change}{100})\)

Problem 1

Old amount \(a = 125\), percent of change \(p=20\)
\(New\ amount=125\times(1 + \frac{20}{100})\)
\(=125\times1.2\)
\(=150\)

Problem 2

Old amount \(a = 42\), percent of change \(p = 0.08\)
\(New\ amount=42\times(1+\frac{0.08}{100})\)
\(=42\times(1 + 0.0008)\)
\(=42\times1.0008\)
\(=42.0336\)

Problem 3

Old amount \(a=5680\), percent of change \(p = 0.5\)
\(New\ amount=5680\times(1-\frac{0.5}{100})\)
\(=5680\times(1 - 0.005)\)
\(=5680\times0.995\)
\(=5651.6\)

Problem 4

Old amount \(a = 452\), percent of change \(p=5.25\)
\(New\ amount=452\times(1+\frac{5.25}{100})\)
\(=452\times(1 + 0.0525)\)
\(=452\times1.0525\)
\(=475.73\)

Problem 5

Old amount \(a = 65\), percent of change \(p = 15\) (decrease)
\(New\ amount=65\times(1-\frac{15}{100})\)
\(=65\times0.85\)
\(=55.25\)

Problem 6

Old amount \(a = 42\), percent of change \(p = 110\) (increase)
\(New\ amount=42\times(1+\frac{110}{100})\)
\(=42\times2.1\)
\(=88.2\)

Answer:

1. \(150\)
2. \(42.0336\)
3. \(5651.6\)
4. \(475.73\)
5. d. \(\$55.25\)
6. e. \(\$88.20\)