Question

Difficulty: HardSimple Interest Applications

Marcus is comparing two personal bank loan options to finance home repairs. Option X offers a $4,000\$4,000 loan at an annual simple interest rate of 6%6\% for 1818 months. Option Y offers a $5,000\$5,000 loan at an annual simple interest rate of 4%4\% for 99 months. How much more interest will Marcus pay with Option X compared to Option Y?

  1. $210\$210Answer
  2. B
    $252\$252
  3. C
    $2,100\$2,100
  4. D
    $2,520\$2,520

Answer

$210\$210
The correct answer accurately converts both time periods into years and applies the simple interest formula (I=P×R×TI = P \times R \times T) to find the interest for both loans before calculating their difference. Option X generates $360\$360 in interest (4000×0.06×1.54000 \times 0.06 \times 1.5), and Option Y generates $150\$150 in interest (5000×0.04×0.755000 \times 0.04 \times 0.75). The difference is $360−$150=$210\$360 - \$150 = \$210.

Step-by-Step Solution

1
Convert the loan durations from months to years by dividing by 12.
Option X time: 18÷12=1.518 \div 12 = 1.5 years. Option Y time: 9÷12=0.759 \div 12 = 0.75 years.
The simple interest formula requires the time to be in the same units as the annual interest rate.
2
Calculate the total simple interest for Option X using I=P×R×TI = P \times R \times T.
IX=$4,000×0.06×1.5=$360I_X = \$4,000 \times 0.06 \times 1.5 = \$360
This determines the exact cost of borrowing for the first option.
3
Calculate the total simple interest for Option Y using I=P×R×TI = P \times R \times T.
IY=$5,000×0.04×0.75=$150I_Y = \$5,000 \times 0.04 \times 0.75 = \$150
This determines the exact cost of borrowing for the second option.
4
Subtract the interest of Option Y from the interest of Option X.
$360−$150=$210\$360 - \$150 = \$210
The question asks for the difference in interest paid between the two options.

Key Concept

Calculating and comparing simple interest across different principals, rates, and fractional year time periods.
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