class 8 NCERT bridge course Answers Activity W2.1: Let us Brainstorm

 Activities for Week 2 

Activity W2.1: Let us Brainstorm

 Students may be given these puzzles to solve. 

They may do it individually or in pairs. 

They may be asked to justify their answers. 

A. Determine the missing value in the puzzle below

☆❒☆❒☆❒☆❒ = 16

☆❒☆❒☆❒☆ = 13

☆❒☆❒ = 8

☆☆☆❒❒❒ = ?

SOLUTION
Let:

• ☆ = x

  
  

• ❒= y

4 stars + 4 squares = 16
4x + 4y = 16
Divide both sides by 4:
x + y = 4 — (Equation 1)

4 stars + 3 squares = 13
4x + 3y = 13 — (Equation 2)

Subtract Equation 1 from Equation 2:
(4x + 3y) - (4x + 4y) = 13 - 16
4x + 3y - 4x - 4y = -3
Simplifies to:
-y = -3
So:
y = 3 (Square = 3)
Substitute into Equation 1:
x + 3 = 4
So:
x = 1 (Star = 1)
 Now solve the last expression:
☆ + ☆ + ☆ + ❒ + ❒ + ❒
= 3x + 3y
= 3(1) + 3(3)
= 3 + 9 = 12

FINAL ANSWER 

☆☆☆❒❒❒ = 12

a) x² - 1 - ( x² + 1) 

= 6² - 1 - (5² +1)

= 36 - 1 - (25 +1)

= 35 - 26
= 9

b) x² - 1 + ( x² + 1) 

= 8² - 1 + (5² +1)

= 64 - 1 + (25 +1)

= 63 + 26
= 89