Belinda borrowed $20,500 at simple interest rate of 4.30% p.a. from her parents to start a business. At the end of 3 months, she paid them $7,100 and $6,900 at the end of 8 months. How much would she have to pay them at the end of 18 months to clear the balance?

interest for 3 months = 20500(.043)(1/4) = 220.375

amount owing at that time = 20720.375
after payment of 7100, amount owing = $13,620.375
interest on the next 5 months = 244.03
debt at the end of that time = $13,864.41
after the 6900 payment, balance at the end
of 8 months = $6,964.41

You finish it ....

find the interest for the next 10 months, add it on the last balance and you are done.

is the final answer $7,213.96?

correct

To find out how much Belinda would have to pay at the end of 18 months, we need to calculate the total balance remaining after the two payments she made.

First, let's calculate the interest on the loan. The simple interest formula is:

Interest = Principal x Rate x Time

For the first payment of $7,100 after 3 months, we can use the formula as follows:

Interest1 = Principal x Rate x Time
Interest1 = $20,500 x (4.30% / 100) x (3 / 12)
Interest1 = $20,500 x 0.043 x 0.25
Interest1 = $222.63

Now let's calculate the balance after the first payment:

Balance1 = Principal + Interest1
Balance1 = $20,500 + $222.63
Balance1 = $20,722.63

For the second payment of $6,900 after 8 months, we can repeat the steps:

Interest2 = Principal x Rate x Time
Interest2 = $20,722.63 x (4.30% / 100) x (8 / 12)
Interest2 = $20,722.63 x 0.043 x 0.667
Interest2 = $601.62

Balance2 = Balance1 + Interest2
Balance2 = $20,722.63 + $601.62
Balance2 = $21,324.25

Now that we know the remaining balance after 8 months, we need to find out how much Belinda would have to pay at the end of 18 months.

To calculate this, we can use the same formula to find the interest for the remaining 10 months:

Interest3 = Balance2 x (4.30% / 100) x (10 / 12)
Interest3 = $21,324.25 x 0.043 x 0.833
Interest3 = $756.06

Finally, let's calculate the total amount Belinda would have to pay at the end of 18 months:

Total Payment = Balance2 + Interest3
Total Payment = $21,324.25 + $756.06
Total Payment = $22,080.31

Therefore, Belinda would have to pay $22,080.31 at the end of 18 months to clear the balance.