Question 7 - Figure it out - Page 102 to 105 - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

Transcript

Question 7 (a) Simplify the following expressions: (a) 3a + 9b – 6 + 8a – 4b – 7a + 16 Now, 3a + 9b – 6 + 8a – 4b – 7a + 16 = (3a + 8a – 7a) + (9b – 4b) + (16 – 6) = (11a – 7a) + 5b + 10 = 4a + 5b + 10 Question 7 (b) Simplify the following expressions: (b) 3 (3a – 3b) – 8a – 4b – 16 Now, 3 (3a – 3b) – 8a – 4b – 16 = 3 × 3a – 3 × 3b – 8a – 4b – 16 = 9a – 9b – 8a – 4b – 16 = 9a – 8a – 9b – 4b – 16 = (9a – 8a) – (9b + 4b) – 16 = a – 13b – 16 Question 7 (c) Simplify the following expressions: (c) 2 (2x – 3) + 8x + 12 Now, 2 (2x – 3) + 8x + 12 = 2 × 2x – 2 × 3 + 8x + 12 = 4x – 6 + 8x + 12 = (4x + 8x) + (12 – 6) = 12x + 6 Question 7 (d) Simplify the following expressions: (d) 8x – (2x – 3) + 12 Now, 8x – (2x – 3) + 12 = 8x – 2x + 3 – 12 = (8x – 2x) + (3 – 12) = (8x – 2x) + (–12 + 3) = (8x – 2x) – (12 – 3) = 6x – 9 Question 7 (e) Simplify the following expressions: (e) 8h – (5 + 7h) + 9 Now, 8h – (5 + 7h) + 9 = 8h – 5 – 7h + 9 = 8h – 7h + 9 – 5 = (8h – 7h) + (9 – 5) = h + 4 Question 7 (f) Simplify the following expressions: (f) 23 + 4(6m – 3n) – 8n – 3m – 18Now, 23 + 4(6m – 3n) – 8n – 3m – 18 = 23 + 4 × 6m – 4 × 3n – 8n – 3m – 18 = 23 + 24m – 12n – 8n – 3m – 18 = 24m – 3m – 12n – 8n + 23 – 18 = (24m – 3m) – (12n + 8n) + (23 – 18) = 21m – 20n + 5