type 1 basic simple interest using formula Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (b)

Using Rule 1,

Let the rate of interest be R per cent per annum.

${400 × 2 × R}/100 + {550 × 4 × R}/100$

+ ${1200 × 6 × R}/100 = 1020$

8R + 22 R +72 R = 1020

102 R= 1020

R = $1020/102$ = 10%

Answer: (b)

Using Rule 1,

4200 = ${29400 × 6 × R}/100$

R = $4200/{294 × 6} = 50/21 = 2{8}/21$%

Answer: (b)

Simple interest for 2 years

= Rs.(568 - 520) = Rs.48

Interest for 5 years

= Rs.$48/2 × 5$ = Rs.120

Principal = Rs.(520 - 120) = Rs.400

Using Rule 12,

P = $({A_2T_1 - A_1T_2}/{T_1 - T_2})$

=$({568 × 5 - 520 × 7}/{5 - 7})$

= $({2840 - 3640}/{-2})$

=${- 800}/{- 2}$ = Rs.400

Answer: (d)

Using Rule 1,

P = ${A × 100}/{100 + r × t}$

=${7000 × 100}/{100 + 10/3 × 5}$

= ${7000 × 100 × 3}/350$ = Rs.6000

Answer: (c)

Using Rule 1,

Let the sum lent to C be x

According to the question,

${2500 × 7 × 4}/100 + {x × 7 × 4}/100 = 1120$

or 2500 × 28 + 28x = 112000

or 2500 + x = 4000

or x = 4000 - 2500 = 1500

Answer: (c)

Principal + interest for 8 years= Rs.2900... (i)

Principal + interest for 10 years = Rs.3000 ... (ii)

Subtracting equation (i) from (ii)

Interest for 2 years = Rs.100

Interest for 8 years

= $100/2 × 8$ = Rs.400

From equation (i),

Principal = Rs.(2900 - 400) = Rs.2500

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

= ${400 × 100}/{8 × 2500} = 2%$

Using Rule 12,

R = $({A_1 - A_2}/{A_2T_1 - A_1T_2})$ × 100

= $({2900 - 3000}/{3000 × 8 - 2900 × 10})$ × 100

=$({- 100}/{24000 - 29000}) × 100$

= ${-100}/{-5000}$ × 100 = 2%