Answer:

(1)The percentage error is 6.897 % .

(2)The total cost of the wallet is $34.35 .

(3)The salesman’s commission as a percent of his total monthly sales is 4% .

(4)The interest is $5400 .

Step-by-step explanation:

First part

Formula

Percentage = frac{Change in valuetimes 100}{Exact value}

Change in value = |Approx value – Exact value|

As given

Mark estimates that the distance from his house to his school is 15.5 mi. The actual distance is 14.5 mi.

Approx value =  15.5 mi

Exact value = 14.5 mi

Change in value = |15.5 – 14.5|

                           = 1

Put all the values in the formula

Percentage error = frac{1times 100}{14.5}

Percentage error = frac{100}{14.5}

Percentage error = 6.897 % (Approx)

Thus the percentage error is 6.897 % .

Second part

The price of a wallet is $31.95 and the sales tax is 7.5%.

7.5% is written in the decimal form

= frac{7.5}{100}

= 0.075

Sales tax price = 0.075 × Price of the wallet

                         = 0.075 × $31.95

                          = $2.4 (Approx)

Total cost of the wallets = Cost of the wallet + Sales tax price

                                        = $31.95 + $2.4

                                        = $34.35

Therefore the total cost of the wallet is $34.35.

Third part

Formula

Percentage = frac{Part valuetimes 100}{Total value}

A sneaker store salesman had $4,125 in total monthly sales last month. He made $165 in commission from those sales.

Part value = $165

Total value = $4125

Put all the values in the formula

Percentage = frac{165times 100}{4125}

Percentage = frac{16500}{4125}

Percentage = 4%

Therefore the salesman’s commission as a percent of his total monthly sales is 4% .

Fourth part

Formula

Simple interest = frac{Principletimes Ratetimes Time}{100}

Principle = $12000

Rate = 15%

Time = 3 years

Put all the values in the formula

Simple interest = frac{12000times 15times 3}{100}

Simple interest = frac{540000}{100}

Simple interest = $5400

Therefore the interest is $5400 .