Example 9 - Chapter 7 Class 8 - Proportional Reasoning-1(Ganita Prakash)

Transcript

Example 9 A car travels 90 km in 150 minutes. If it continues at the same speed, what distance will it cover in 4 hours? To do this, first we convert units as same This means Both units of Distance will be in km Both units of time will be in minutes Since 4 hours = 4 × 60 = 240 minutes Our question becomes A car travels 90 km in 150 minutes. If it continues at the same speed, what distance will it cover in 240 minutes Now, In 150 minutes, car travels 90 km So, the ratio of Distance to Time is 90 : 150 Now, we need to find Distance travelled in 240 minutes So, the ratio of Distance to Time is Distance : 240 Since Speed is same in both cases Both these Ratios will be Proportional So, we write 90 : 150 :: Distance : 240 Converting into fractions 𝟗𝟎/𝟏𝟓𝟎=𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆/𝟐𝟒𝟎 Cross multiplying 90/150 × 240 = Distance Distance = 90/150 × 240 Distanc = (9 × 240)/15 Distance = (3 × 240)/5 Distance = 3 × 48 Distance = 144 Thus, distance covered by the car in 4 hours is 144 km