Rekhadidi deposited ₹ 10000 of her savings in two separate banks at the same time. The rate of simple interest per annum is 6% in one bank and 7% in another bank; After 2 years, if she gets ₹1280 in total as interest, then let us write by calculating, the money she had deposited separately in each of the two banks.

For Bank – 1:

Principal (P) = x

rate (r) = 6 %

time (t) =  2 yr

SI = x × 6 × 2\over 100 = 12x\over 100

For Bank – 2:

Principal (P) = 10000 – x

rate (r) = 7 %

time (t) =  2 yr

SI = (10000 - x) × 7 × 2\over 100 = 14(10000 - x)\over 100

According to the problem,

₹ {\frac{x × 6 × 2}{100}+\frac{(10000-x) × 7 × 2}{100}} = ₹ 1280

or, \frac{12x}{100}+\frac{14(10000-x)}{100} = 1280

or, \frac{12x+140000-14 x}{100} = 1280

or, -2x + 140000 = 1280 × 100

or, 140000 – 128000 = 2x

∴ x = \frac{12000}{2} = 6000

∴ She deposited ₹ 6000 in the 1st bank & ₹ 4000 in the 2nd bank.