Question 1 - Mind the Mistake, Mend the Mistake (Page 94) - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

Transcript

Question 1 Observe each of them and see if there is a mistake. If you think there is a mistake, try to explain what might have gone wrong. Then, simplify it correctly. Let’s do it one by one For (1) Expression is 3a + 2b This is in its simplest form. So, correct simplest form is 3a + 2b For (2) Expression is 3b – 2b – b = 3b – (2b + b) = 3b – 3b = 0 So, correct simplest form is 0 Which was also the given simplest form For (3) Expression is 6(p + 2) = 6p + 6 × 2 = 6p + 12 So, correct simplest form is 6p + 12 For (4) Expression is (4x + 3y) – (3x + 4y) = 4x + 3y – 3x – 4y = (4x – 3x) + (3y – 4y) = x – (–3y + 4y) = x – (4y – 3y) = x – y So, correct simplest form is x – y For (5) Expression is 5 – (2 – 6z) = 5 – 2 + 6z = 3 + 6z So, correct simplest form is 3 + 6z For (6) Expression is 2 + (x + 3) = x + (2 + 3) = x + 5 So, correct simplest form is x + 5 For (7) Expression is 2y + (3y – 6) = (2y + 3y) – 6 = 5y – 6 So, correct simplest form is 5y – 6 For (8) Expression is 7p – p + 5q – 2q = (7p – q) + (5q – 2q) = 6p + 3q So, correct simplest form is 6p + 3q For (9) Expression is 5 (2w + 3x + 4w) = 5 (2w + 4w + 3x) = 5 (6w + 3x) = 5 × 6w + 5 × 3x = 5 × 6 × w + 5 × 3 × x = 30w + 15x So, correct simplest form is 30w + 15x Which is same as given simplest form 10w + 15x + 20w = 10w + 20w + 15x = 30w + 15x For (10) Expression is 3j + 6k + 9h + 12 = 3j + 3 × 2k + 3 × 3h + 3 × 4 = 3 (j + 2k + 3h + 4) So, correct simplest form is 3 (j + 2k + 3h + 4) Which is same as given simplest form 3 (j + 2k + 3h + 4) For (11) Expression is 4 (2r + 3x + 5) = 4 × 2r + 4 × 3x + 4 × 5 = 8r + 12x + 20 So, correct simplest form is 8r + 12x + 20