(i) By Inverse proportion
3 × 4 = 4 × (no. of days required)
(No. of days required) = \(\frac{3\,\times\,4}{4}\) = 3 days
(ii) By Inverse proportion
5 × 144 = 6 × (time required)
(Time required) = \(\frac{5\,\times144}{6}\) = 120 minutes
(iii) By Inverse proportion
90 minutes × 60 km/hr = 45 km/hr × (time taken in minutes)
(No. of days required) = \(\frac{90\,\times\,60}{45}\) = 120 minutes = 2 hours
(iv) More the oranges more will be the cost. So it is a direct proportion.
Let the cost be Rs x, \(\frac{20.80}{8}=\frac{x}{5}\)
⇒ 8 × x = 20.80 × 5
x = \(\frac{20.80\,\times\,5}{8}\) = Rs 13
(v) More the no. of sheets more will be the weight of them. So it is a direct proportion.
Let the no. of sheets be x, \(\frac{12}{50}=\frac{\text{x}}{500}\)
50 × x = 500 × 12
x = \(\frac{500\,\times\,12}{50}\) = 120 sheets