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

Answer: (b)

Using Rule 1,

Interest = Rs.(81–72)= Rs.9

Let the time be t years.

Then, 9 = ${72 × 25 × t}/{4 × 100}$

t = ${9 × 400}/{72 × 25}$ = 2 years.

Answer: (c)

Using Rule 1,

The sum of money will give Rs.365 as simple interest in a year.

S.I. = $\text"PRT"/100$

365 = ${P × 5 × 1}/100$

P = ${365 × 100}/5$ = Rs.7300

Answer: (d)

Using Rule 1,

S.I. = 956 - 800 = Rs.156

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

= ${156 × 100}/{800 × 3}$ = 6.5% per annum

New rate = 10.5%

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

= ${800 × 3 × 10.5}/100$ = Rs.252

Amount = 800 + 252 = Rs.1052

Answer: (d)

Using Rule 1,

Principal (P) = Rs.1600

T = 2 years 3 months

= $(2 + 3/12) yrs. = (2 + 1/4) yrs. = 9/4 yrs.$

S.I = Rs.252

R = % rate of interest per annum

R = ${100 × S.I.}/{P × t}$

= ${100 × 252}/{1600 × 9/4}$

Rate of interest = 7% per annum.

Answer: (d)

Using Rule 1,

Let the sum lent at 4% = Rs.x

Amount at 5%= (16000 - x )

According to the question,

${x × 4 × 1}/100 + {(16000 - X) × 5 × 1}/100$ = 700

4x + 80000 - 5x = 70000

x = 80000 - 70000 = Rs.10000

Answer: (c)

S.I. for 1$1/2$ years

= Rs.(873 - 756) = Rs.117

S.I. for 2 years

= Rs.$(117 × 2/3 × 2)$ = Rs.156

Principal = 756 - 156 = Rs.600

Now, P = 600, T = 2, S.I. = 156

R = ${100 × S.I.}/{P × T}$

= ${100 × 156}/{600 × 2}$ = 13%

Using Rule 12,

Rate of interest

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

= $({756 - 873}/{873 × 2 - 756 × 7/2}) × 100$

= $({- 117}/{1746 - 2646}) × 100$

= $({- 117}/{- 900})$ × 100 = 13%