Answer:
p = $12,000
c = $4,500
b = $3,000
Step-by-step explanation:
Denote the variables as follows:
p = amount borrowed from parents
c = amount borrowed from the credit union
b = amount borrowed from the bank
The equations that can be formed using the given information are as follows:
p + c + b = 19500... (i)
p = 4b... (ii)
The formula to compute simple interest is:
SI = P × (R/100) × T
So, the equation for the total interest paid at the end of 1 year is:
0.05p + 0.04c + 0.03b = 870
5p + 4c + 3b = 87000... (iii)
Substitute (ii) in (i) and (iii) and simplify as follows:
4b + c + b = 19500
⇒ c + 5b = 19500... (iv)
5(4b) + 4c + 3b = 87000
⇒ 4c + 23b = 87000... (v)
Subtract (iv) from (v):
4c + 23b = 87000
(-)c + (-)5b = (-)19500 ] × 4
⇒
4c + 23b = 87000
-4c - 20b = -78000
⇒
3b = 9000
b = 3000
Compute the value of p as follows:
p = 4b = 4 × 3000 = 12000
p = 12000
Compute the value of c as follows:
p + c + b = 19500
12000 + c + 3000 = 19500
c + 15000 = 19500
c = 4500
Thus, the amount borrowed from each source is:
p = $12,000
c = $4,500
b = $3,000