Question

interest on rs. a at the simple interest 10% pre annum for b mounth is

Answer 1

Hey friend ..
Formula for simple intrest
SI = P×R×T/100

Where. SI = simple intrest
P = principle
R = rate percentage for a year
T = duration in years ( in case of month we can devide it by 12 to convert it in year )

Now. Put given values in equation

SI = a×10×b/100 ×12
= ab/120

Hope it will help you !!

Answer 2

Clearly, Rate = 5% p.a., Time = 3 years, S.I.= Rs. 1200. . .
So principal=RS [100*1200]/3*5=RS 8000
Amount = Rs. 8000 x [1 +5/100]^3 - = Rs. 9261.
.. C.I. = Rs. (9261 - 8000) = Rs. 1261.