Question

A sum when reckoned at 7-1/2% per annum amounts to 3920 in 3 years. Find the sum
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Answer 1

P=principal=sum

R=rate of interest= 7½ %=7.5 %=0.075

T=time in year=3yrs

S.I=P*R*T

S.I = P*0.075*3=0.225P

Amount is given 3920

Amount=Principle +simple interest

3920=P+0.225P

3920=P(1+0.225)

3920=P(1.225)

3920/1.225=P

3200=P

P=sum= $3200

Answer 2

Answer:

3200

Step-by-step explanation:

LET PRINCEPAL=X,

SI=AMOUNT-PRINCIPAL,

SI=3920-X,

RATE=7-1/2%=7.5%,

P=SI*100/RATE*TIME,

X=3920-X*100/7.5*3,

X=3920-X*100*10/75*3,

X=3920-X*20*2/3*3,

X=3920-X*40/9,

X=156800-40X/9,

9X=156800-40X,

9X+40X=156800,

49X=156800,

X=156800/49=3200