how to change the sabject if the formula if A=p(i+rt)

Question

Quantitative methods

Answer 1

If we take each variable in turn, this will illustrate the method generally.

p: divide through by i+rt: p=A/(i+rt).

i: i+rt=A/p, i=A/p-rt=(A-prt)/p.

r: i+rt=A/p, rt=A/p-i=(A-ip)/p, r=(A-ip)/pt.

t: t=(A-ip)/pr.

[This looks a bit like A=p+ptr=p(1+rt), where p is a principal amount invested at a simple interest rate of r for a period t. The interest i=ptr, so A=p+i. It may be that the question formula should have been A=p(1+rt) rather than A=p(i+rt). If this is the case then substitute 1 for i in the above, so ip becomes p.]