model 3 combination of si & ci Section-Wise Topic Notes With Detailed Explanation And Example Questions

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: (d)

Principal = $\text"S.I. × 100"/ \text"Time × Rate"$

= ${50 × 100}/{2 × 5}$ = Rs.500

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

= 500$[(1 + 5/100)^2 - 1]$

= 500$[(1 + 1/20)^2 - 1]$

= 500$[(21/20)^2 - 1]$

= 500$(441/400 - 1)$

= ${500 × 41}/400$ = Rs.51.25

Answer: (c)

Since, S.I. for 3 years = Rs.240

S.I. for 2 years = $240/3$× 2 = Rs.160

${PR × 2}/100$ = 160

PR = 160 × 50 = 8000...(i)

Again, C.I. - S.I. = 170 - 160 = Rs.10

${PR^2}/10000$ = 10

${8000 × R}/10000$ = 10

R = $100/8 = 25/2 = 12{1}/2$%