T is your sister's birthday and you are preparing a family meal. The joint of meat needs to be cooked for 30 minutes per 500 g plus an extra 20 minutes. How long will it take to cook a joint of meat weighing 2.5 kilograms?

1 kg = 1000 g ... so 2.5 kg = (2.5 * 1000) = 2500 grams

it cooks 30 minutes per 500 g ... 2500/500 = 5 ... so there are 5 thirty minute periods ... (5 * 30) = 150 minutes ... plus the extra 20 minutes ... (150 + 20) = 170 minutes ... so your answerr is 2 hrs 50 minutes