model 3 combination of si & ci Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (a)

Using Rule 1,

C.I. = P$[(1 + R/100)^T - 1]$

246 = P$[(1 + 5/100)^2 - 1]$

246 = P$[(21/20)^2 - 1]$

246 = P$({441 - 400}/400)$

246 = ${41P}/400$

P = ${246 × 400}/41$ = Rs.2400

SI = $\text"Principal × Time × Rate"/100$

= ${2400 × 3 × 6}/100$ = Rs.432

Answer: (a)

If the principal be P then

C.I. = P$[(1 + R/100)^T - 1]$

420 = P$[(1 + 10/100)^2 - 1]$

420 = P$({121 - 100}/100)$

420 = ${P × 21}/100$

P = ${420 × 100}/21$ = Rs.2000

S.I. = ${PRT}/100 = {2000 × 10 × 2}/100$ = Rs.400

Using Rule 10,

Here, C.I. = Rs.420, R = 10%, S.I. = ?

C.I. = S.I.$(1 + R/200)$

420 = S.I.$(1 + 10/200)$

420 = S.I.$(210/200)$

S.I. = ${420 × 200}/210$ = Rs.400