Question 8 - Figure it out - Page 102 to 105 - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

Transcript

Question 8 (a) Add the expressions given below: (a) 4d – 7c + 9 and 8c – 11 + 9dNow, (4d – 7c + 9) + (8c – 11 + 9d) = 4d – 7c + 9 + 8c – 11 + 9d = 4d + 9d + 8c – 7c + 9 – 11 = 4d + 9d + 8c – 7c – 11 + 9 = (4d + 9d) + (8c – 7c) – (11 – 9) = 13d + c – 2 Question 8 (b) Add the expressions given below: (b) – 6f + 19 – 8s and – 23 + 13f + 12s Now, (–6f + 19 – 8s) + (–23 + 13f + 12s) = –6f + 19 – 8s – 23 + 13f + 12s = 13f – 6f + 12s – 8s – 23 + 19 = (13f – 6f) + (12s – 8s) – (23 – 19) = 7f + 4s – 4 Question 8 (c) Add the expressions given below: (c) 8d – 14c + 9 and 16c – (11 + 9d) Now, (8d – 14c + 9) + (16c – (11 + 9d)) = 8d – 14c + 9 + 16c – (11 + 9d) = 8d – 14c + 9 + 16c – 11 – 9d = – 9d + 8d + 16c – 14c – 11 + 9 = –(9d – 8d) + (16c – 14c) – (11 – 9) = –d + 2c – 2 Question 8 (d) Add the expressions given below: (d) 6f – 20 + 8s and 23 – 13f – 12s Now, (6f – 20 + 8s) + (23 – 13f – 12s) = 6f – 20 + 8s + 23 – 13f – 12s = –13f + 6f – 12s + 8s + 23 – 20 = –(13f – 6f) – (12s – 8s) + (23 – 20) = –7f – 4s + 3 Question 8 (e) Add the expressions given below: (e) 13m – 12n and 12n – 13m Now, (13m – 12n) + (12n – 13m) = 13m – 12n + 12n – 13m = 13m – 13m + 12n – 12n = (13m – 13m) + (12n – 12n) = 0 + 0 = 0 Question 8 (f) Add the expressions given below: (f) – 26m + 24n and 26m – 24nNow, (–26m + 24n) + (26m – 24n) = – 26m + 24n + 26m – 24n = (26m – 26m) + (24n – 24n) = 0 + 0 = 0