type 3 money multiples in ‘n’ years Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (d)

Let the principal be x.

Case-I

$2x = {x × R × 15}/100$

R = ${2 × 100}/15 = 40/3%$

Case-II

SI = 4x

$4x = {x × 40 × T}/300$

T = ${4 × 300}/40 = 30$ years

Using Rule 3,

R = ${(3 - 1)}/15 × 100%$

= $2/15 × 100%$

= $2/3 × 20% = 40/3%$

T = ${(n - 1)}/R$ Years

= ${(5 - 1)}/{40/3} × 100$ = 30 years.

Answer: (b)

Principal = P

Amount = ${7p}/6$

S.I. = ${7p}/6 - P = P/6$

R = ${S.I × 100}/{P × T} = {P × 100}/{6 × p × 3}$

= $50/9 = 5{5}/9%$

R% = ${(7/6 - 1) × 100%}/3$

= $1/18 × 100% = 50/9%$

= 5$5/9$%

Answer: (c)

Principal = Rs.P and time = T years

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

According to the question,

P + ${PT × 5}/100$ = 2200

P + ${PT}/20$ = 2200 ...(i)

Again, ${PT × 8}/100 - {PT × 5}/100$

= 2320 - 2200

${3PT}/100$ = 120

PT = ${120 × 100}/3$ = 4000 ...(ii)

From equation (i),

P + $4000/20$ = 2200

P = 2200 - 200 = Rs. 2000

From equation (ii),

PT = 4000

T = $4000/2000$ = 2 years

Alternative Method

Difference in rates

= 8 - 5 = 3%

Since,3% ≡ 2320 - 2200 = 120

5% ≡ $120/3$ × 5 = 200

Principal = Rs.(2200 - 200) = Rs.2000

Time = ${200 × 100}/{2000 × 5}$ = 2 years

Answer: (a)

Principal = Rs.x

Amount = Rs.2x

Interest = 2x - x = Rs.x

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

= ${x × 100}/{x × 8} = 25/2$ = 12.5 % per annum

Using Rule 3,

R % = ${(n - 1)}/T × 100%$

= ${(2 - 1)}/8 × 100%$ = 12.5%

Answer: (b)

According to the question,

If principal be Rs. x, then

S.I. = Rs. x

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

= ${x × 100}/{x × 25/4} = 400/25$ = 16 years

Using Rule 3,

T = ${(n - 1)}/R × 100%$

= ${2 - 1}/{25/4} × 100$

= $400/25$ = 16 years.

Answer: (d)

TIme = ${SI × 100}/\text"Principal × Rate"$

= ${x × 100}/{x × 25/4}$ = 16 years

Using Rule 3,

T = ${(n - 1)}/{R%} years$

= ${(2 - 1)}/{25/4} × 100$ years = 16 years.