Area

The cost price of 20 articles is the same as the selling price of x articles. If the profit is 25%, then the value of x is:

Answer: (b)

Let C.P. of each article be Rs. 1  C.P. of x articles = Rs. x.

S.P. of x articles = Rs. 20.

Profit = Rs. (20 - x).

∴ \(\frac{20 - x}{x} \times 100 = 25\)

⇒ 2000 - 100x = 25x

⇒ 125= 2000

= 16

Jo’s collection contains US, Indian and British stamps. If the ratio of US to Indian stamps is 5 to 2 and the ratio of Indian to British stamps is 5 to 1, what is the ratio of US to British stamps?

Answer: (d)

Indian stamps are common to both ratios. Multiply both ratios by factors such that the Indian stamps are represented by the same number.

US : Indian = 5 : 2, and

Indian : British = 5 : 1.

Multiply the first by 5, and the second by 2.

Hence the two ratios can be combined and

US : British = 25 : 2

Now,

US : Indian = 25 : 10, and

Indian : British = 10 : 2

A bag contains 50 P, 25 P and 10 P coins in the ratio 5 : 9 : 4, amounting to Rs. 206. Find the number of coins of each type respectively.

Answer: (c)

Let ratio be x.Hence no. of coins be 5x ,9x , 4x respectively.

Now given total amount
= Rs. 206 ⇒ (.50)(5x) + (.25)(9x) + (.10)(4x)

= 206 we get x = 40 ⇒ No. of 50p coins

= 200

⇒ No. of 25p coins = 360

⇒ No. of 10p coins = 160

Fresh fruit contains 68% water and dry fruit contains 20% water. How much dry fruit can be obtained from 100 kg of fresh fruits ?

Answer: (c)

The fruit content in both the fresh fruit and dry fruit is the same.

Given, fresh fruit has 68% water. so remaining 32% is fruit content. weight of fresh fruits is 100 kg.

Dry fruit has 20% water. so remaining 80% is fruit content.

Let weight if dry fruit be y kg.

fruit % in fresh fruit = fruit % in dryfruit

 (32/100) × 100 = (80/100 ) × y

we get, y = 40 kg

The area of a rectangle is 460 square metres. If the length is 15% more than the breadth, what is the breadth of the rectangular field ?

Answer: (b)

Let breadth = x metres.
Then length =(115x/100) metres.

x × (115x/100) = 460

⇒ x2 = (460 × 100/115)

⇒ x2 = 400

⇒ x = 20

A man walked diagonally across a square lot. Approximately, what was the percent saved by not walking along the edges?

Answer: (a)

Let the side of the square(ABCD) be x meters.

Then, AB + BC = 2x metres.

AC =  √2x = (1.41x) m.

Saving on 2x metres = (0.59x) m.

Saving % = (0.59x/2x) × 100 % =30% (approx)

A tank is 25m long 12m wide and 6m deep. The cost of plastering its walls and bottom at 75 paise per sq. m is

Answer: (d)

Area to be plastered
= [2 (l + b) × h] + (l × b)
= [2 (25 + 12) × 6] + (25 × 12)
= 744 sq. m

Cost of plastering = 744 × (75/100)
= Rs. 558

If the radius of a circle is decreased by 50%, find the percentage decrease in its area.

Answer: (c)

Let original radius = R.

New radius =b(50/100) R = (R/2)

Original area ΠR2 and new area= \(\pi \left ( \frac{R}{2} \right )^{2} = \frac{\pi R^{2}}{4}\)

Decrease in area

= \(\frac{3\pi R^{2}}{4} \times \frac{1}{\pi R^{2}} \times 100\)

= 75%

If each side of a square is increased by 25%, find the percentage change in its area?

Answer: (b)

Let each side of the square be a,

then area = a × a

New side = 125a/100 = 5a/4

New area = (5a × 5a) / (4 × 4)

= (25a²/16)

increased area== (25a²/16) - a²

Increase % = [(9a²/16 ) × (1/a² ) × 100] %

= 56.25%

The diagonal of a rectangle is √41 cm and its area is 20 sq. cm. The perimeter of the rectangle must be:

Answer: (a)

Let \(\sqrt{l^{2} + b^{2}} = \sqrt{41}\)

Also, lb = 20

(l + b)2 = l2 + b2 + 2lb
= 41 + 40 = 81

⇒ (l + b) = 9
∴ Perimeter = 2(l + b) = 18 cm.