3Number 3ExplanationThe relationship between speed and travel time of car brand A is presented in the table below. Speed60 km/h60 \text{ km/h}60 km/h72 km/h72 \text{ km/h}72 km/h96 km/h96 \text{ km/h}96 km/hTime1 hour 36 minutes1 \text{ hour } 36 \text{ minutes}1 hour 36 minutes...1 hour1 \text{ hour}1 hour The time required if the car is driven at a speed of 72 km/h72 \text{ km/h}72 km/h is ....111 hour 151515 minutes111 hour 202020 minutes111 hour 303030 minutes111 hour 404040 minutes111 hour 454545 minutesExplanationThe relationship between speed (vvv) and time (ttt) is inversely proportional. This means the product of speed and time is constant (fixed distance). v1×t1=v2×t2v_1 \times t_1 = v_2 \times t_2v1×t1=v2×t2 From the table, we know: First speed v1=96 km/hv_1 = 96 \text{ km/h}v1=96 km/h First time t1=1 hourt_1 = 1 \text{ hour}t1=1 hour Second speed v2=72 km/hv_2 = 72 \text{ km/h}v2=72 km/h We want to find the second time (t2t_2t2). 96×1=72×t296 \times 1 = 72 \times t_296×1=72×t296=72×t296 = 72 \times t_296=72×t2t2=9672t_2 = \frac{96}{72}t2=7296t2=43 hourst_2 = \frac{4}{3} \text{ hours}t2=34 hours We convert the fraction of an hour into hours and minutes. t2=113 hourst_2 = 1 \frac{1}{3} \text{ hours}t2=131 hourst2=1 hour+(13×60) minutest_2 = 1 \text{ hour} + \left(\frac{1}{3} \times 60\right) \text{ minutes}t2=1 hour+(31×60) minutest2=1 hour 20 minutest_2 = 1 \text{ hour } 20 \text{ minutes}t2=1 hour 20 minutes Thus, the time required is 1 hour 20 minutes1 \text{ hour } 20 \text{ minutes}1 hour 20 minutes.
