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

Answer: (b)

Using Rule 1,

A = P$(1 + R/100)^T$

Let rate be 'r'

${1102.50}/1000 = (1 + r/100)^2$

$11025/10000 = (1 + r/100)^2$

$(105/100)^2 = (1 + r/100)^2$

1 + $r/100 = 105/100$

$r/100 = 5/100$ = 5%

Answer: (b)

Using Rule 1 and 2,

Let the required time be t years. Interest is compounded half yearly.

Time = 2t half years and rate

= $20/2$ = 10%

1000$(1 + 10/100)^{2t}$ = 1331

$(11/10)^{2t} = 1331/1000$

$(11/10)^{2t} = (11/10)^3$ ⇒ 2t = 3

t = $3/2$ years or 1$1/2$ years

Answer: (c)

Using Rule 1,

A = P$(1 + R/100)^T$

30000 + 4347 = $30000(1 + 7/100)^T$

$34347/30000 = (107/100)^T$

$11449/10000 = (107/100)^2 = (107/100)^T$

Time = 2 years

Answer: (c)

Amount = P$(1 + R_1/100)(1 + R_2/100)(1 + R_3/100)$

= 10000$(1+ 4/100)(1 + 5/100)(1 + 6/100)$

= $10000 × 26/25 × 21/20 × 53/50$

A = Rs.11575.2

C.I. = Rs.(11575.2–10000) = Rs.1575.2

Answer: (b)

Using Rule 1 and 2,

Time = t half year

and R = 5% per half year

A = P$(1 + R/100)^T$

$92610/80000 = (1 + 5/100)^T$

$9261/8000 = (21/20)^T$

T = 3 half years or 1$1/2$ years

$(21/20)^3 = (21/20)^T$