Answer:
2 hours 50 minutes.
Explanation:
It is given that the joint of meat needs to be cooked for 30 minutes per 500 grams plus an extra 20 minutes.
Fixed time = 20 minutes
Variable time = 30 minutes per 500 grams
We know that
1 kilogram = 1000 grams
2.5 kilogram = 2500 grams
According to the given information
500 grams = 30 minutes
Multiply both sides by 5.
2500 grams = 150 minutes
It means variable time for 2.5 kg is 150. Total time to cook a joint of meat weighing 2.5 kilograms is
Total time = 150+20 = 170 minutes
We know that 1 hour = 60 minutes.
Total time = 2 hours 50 minutes
Therefore, it will take 2 hours 50 minutes to cook a joint of meat weighing 2.5 kilograms.