type 3 money multiples in ‘n’ years Practice Questions Answers Test with Solutions & More Shortcuts

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: (a)

Case I

Principal = Rs. x

Interest = Rs. x

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

= ${x × 100}/{x × 16} = 25/4%$ per annum

Case II

Interest = Rs. 2x

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

= ${2x × 100 × 4}/{x × 25}$ = 32 years

Using Rule 3,

R = ${(n - 1)}/T × 100%$

= ${(2 - 1)}/16 × 100%$

= $25/4 % = 6{1}/4%$

Now, T = ${(n - 1)}/R × 100%$

= ${(3 - 1)}/{25/4} × 100$

= $800/25$ = 32 years.

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