Question

Add the following rational numbers:

(i) (3/4) and (-3/5)

(ii) -3 and (3/5)

(2 marks)

Answer 1

(i) Given (3/4) and (-3/5)

If p/q and r/s are two rational numbers such that q and s do not have a common factor other than,

(p/q) + (r/s) = (p × s + r × q)/ (q × s)

(0.5 marks)

(3/4) + (-3/5) = (3 × 5 + (-3) × 4)/ (4 × 5)

= (15 – 12)/ 20

= (3/20)

(0.5 marks)

(ii) Given -3 and (3/5)

If p/q and r/s are two rational numbers such that q and s do not have a common factor other than,

(p/q) + (r/s) = (p × s + r × q)/ (q × s)

(0.5 marks)

(-3/1) + (3/5) = (-3 × 5 + 3 × 1)/ (1 × 5)

= (-15 + 3)/ 5

= (-12/5)

(0.5 marks)