Expressions using Letter Numbers Class 7 Short Question Answer

Expressions using Letter Numbers Class 7 Short Question Answer

Expressions using Letter Numbers Class 7 Short Question Answer

Question 1.

The price of rice is ₹ 70 per kg and that of sugar is ₹ 40 per kg. Write an expression for the cost (in ₹) of (x + 5) kg rice and (y + 6) kg sugar and simplify it.

Solution:

Cost of rice (in ₹) = 70 × (x + 5)

Cost of sugar (in ₹) = 40 × (y + 6)

Thus, required expression

= 70 × (x + 5) + 40 x (y + 6)

= 70x + 350 + 40y + 240

= 70x + 40y + 350 + 240

= 10x + 40y + 590.

Question 2.

Simplify the expression :

x + y (3 - 27) - (y + 12) - (4x - 3y).

Solution:

Given expression

= x + y (3 - 27) - (y + 12) - (4x - 3y)

= x + y (- 24) - y - 12 - 4x + 3y

= x - 24y - y - 12 - 4x + 3y

= x - 4x - 24y - y + 3y - 12

= - 5x - 22y - 12.

Question 3.

Ramesh’s father age (in years) is 2 years more than four times Ramesh age. Find the sum of their ages (in years).

Solution:

Let Ramesh age = x years

So, his father age = (4x + 2) years Sum of their ages (in years)

= x + (4x + 2)

= x + 4x + 2

= 5x + 2.

Question 4.

Simplify 6 (2x - 1) - 3 {x + 4).

Solution:

6 (2x - 1) - 3 (x + 4)

= 12x - 6 - 3x - 12

= 12x - 3x - 6 - 12

= 9x - 18.

Question 5.

Given below a pattern created by using different number of matchsticks :

(i) Identify the pattern indicating the number of matchsticks used in each picture.

(ii) How many matchsticks will be used in 6th picture ?

Solution:

(i) Pattern is 2, 4, 6, 8,

So, in nth picture, number of matchsticks used will be 2 × n = 2n.

(ii) In the 6th picture, number of matchsticks used will be 2 × 6 = 12.