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

Answer: (d)

If principal be x, interest = x

and rate = r% p.a. then

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

= ${x × 100}/{x × 10}$ = 10%

Now, p = x, interest = 2x

Then, time = ${SI × 100}/\text"Principal × Rate"$

= ${2x × 100}/{x × 10}$ = 20 years

Using Rule 3,

R = ${(2 - 1)}/10$ × 100%

R = 10%

T = ${(n - 1)}/R × 100$ years

= ${3 - 1}/10 × 100$ = 20 years.

Answer: (d)

Let the principal be x.

Amount = 2x

Interest = (2x - x) = x

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

= ${x × 100}/{x × 12} = 25/3 = 8{1}/3%$

Using Rule 3,

R = ${(2 - 1)}/12 × 100%$

R = $25/3% = 8{1}/3$%

Answer: (d)

Let the principal be x

Principal + SI = ${7x}/4$

SI = ${7x}/4 - x = {3x}/4$

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

= ${3x × 100}/{4 × x × 4} = 18{3}/4%$

Using Rule 3,

R = ${(7/4 - 1)}/4 × 100%$

= $3/16$ × 100%

= $75/4% = 18{3}/4%$

Answer: (b)

Let the principal be Re.1

S.I. = $41/40 - 1 = 1/40$

Now, rate = ${\text"Interest" ×100}/{\text"Principal × Time"}$

= ${1/40 × 100}/{1 × 1/4} = {100 × 4}/40$ = 10%

Using Rule 3,

R = ${(41/40 - 1) × 100%}/{1/4}$

= $1/40 × 4 × 100%$ = 10%

Answer: (a)

Using Rule 1,

SI = Rs.(7200–6000) = Rs.1200

SI = $\text"PRT"/100$

1200 = ${6000 × R × 4}/100$

R = ${1200 × 100}/{6000 × 4}$ = 5%

New rate of R = 5×1.5 = 7.5%

Then, SI = ${6000 × 7.5 × 5}/100$ = Rs.2250

Amount = Rs.(6000 + 2250) = Rs.8250