Exercise

A man spends 1/3 of his salary on food, and 2/5 on house rent. Then he saves an amount of Rs 2000 per month. What is his monthly salary?

Let his salary be x His saving is

x - x/3 - 2x/5

= 15x - 5x - 6x/15 = 4x/15

Because, 4x/15 = 2000

Therefore, x = 15x2000/4 = 7500

A, B and C have to distribute Rs 1200 among them selves. ' A and 'C together have Rs 700 and ' B ' and 'C have Rs 800. How much amount does 'C have ?

A + B + C = 1200

Therefore, A + B + 2C = 700 + 800 = 1500

Therefore, 1200 - C + 2C = 1500

Therefore, C = 1500 - 1200 = 300

The sum of two numbers is 28 and their difference is 4. What is the product of the two numbers ?

Because (x + y)^{2} = (x - y)^{2} + 4xy

x + y = 28, x - y = 4

Therefore, 4xy = (28)^{2} - (4)^{2}

Therefore, (28 + 4)(28 - 4)

Therefore, xy = 32 x 24/4 = 32 x 6 = 192

The ratio of the sum and the difference of two numbers is 3 : 1. Then what is the ratio of these two numbers ?

Let the numbers be x and y

x + y/x - y = 3/1

Therefore, x + y = 3x - 3y

Therefore, 2x = 4y

Therefore, x/y = 4/2 = 2/1

The cost of 16 pens and 12 pencils is Rs 720. What is the cost of 20 pens and 15 pencils ?

Let the price of a pen be x and that of a pencil be y

Therefore, 16x + 12y = 720

Therefore, 16x x 5/4 + 12y x 5/4 = 720 x 5/4

= 20x + 15y = 900

In an examination it is required to get 40% of the aggregate marks to pass. A student got 220 marks and was declared failed by 20 marks. What is the maximum aggregate marks a student can get ?

Because, 40% of total marks = 220 + 20 = 240

Therefore, Total marks = 240/40 x 100 = 600

What is the next number in the sequence? 17, 24, 18, 23, 19, ?

The sequence is +7, -6, +5, -4, +3,................

The difference between 68% of a number and 48% of the same number is 880. Then what is 7% of that number ?

Let the no. be x

Therefore, 68% of x = 48% of x = 880

Therefore, 20/100 x x = 880

Therefore, x = 88000/20 = 4400

Therefore, 7% of 4400 = x 7/100 = 308

Which number should replace both the (?) marks in the following equations?

?/387 = 43/?

?/387 = 43/? Therefore, (?)^{3} = 387 x 43

Therefore, ? = √387 x 43 = √43 x 9 x 43 = 43 x 3 = 129

The daily wages are increased by 25% and a person now gets Rs 60 per day. What was his previous daily wages (in Rs) ?

Let the previous wages be x

Therefore, x + 25/100x x = 60

= 5x/4 = 60 Therefore, x = 48