Independent solution

How to solve this Loan Rate from Principal Portions question

Setup

Setup

For a level-payment loan, principal portions increase geometrically. Use the ten-period principal difference and the principal amount five periods later to identify v.

P(1v10)=3600,Pv5=4871P(1-v^{10})=3600,\quad Pv^5=4871

Model

Model

The two relations give v⁵ = 0.69656 and hence i = 7.5%. The amount 3,600 equals one interest-rate multiple of the requested loan quantity X.

v5=0.69656,i=0.075v^5=0.69656,\quad i=0.075

Compute

Compute

Therefore X = 3,600/0.075 = 48,000.

X=3600/i=48000X=3600/i=48000

Answer

Answer

The calculation gives 48,000 for loan rate from principal portions, matching published choice D.

X=48000(D)\boxed{X=48000\quad\text{(D)}}