Talil is going to make some concrete mix. He needs to mix cement, sand and gravel (1: 3:5) by weight. Talil wants to make 180 kg of concrete mix. He has 15 kg of cement, 85 kg of sand, 100 kg of gravel. Does he have enough to make the concrete?

In order to answer this question you need to find out how much cement, sand and gravel is needed to make 180kg of concrete mix. To do this you must find out how many parts the concrete mix ratio is made up (1+3+5=9). Then divide the total concrete mix (180kg) by the number of parts; 180/9 = 20. This tells you that each of the 9 parts of the ratio = 20kg. As the ratio tells you cement is 1 part you times this by 20kg (1 x 20kg = 20kg). For sand, the ratio tells you sand is 3 parts of the ratio so you times this by 20kg (3 x 20kg = 60kg). Then, for gravel this is 5 parts of the ratio so you times this by 20kg (5x20kg = 100kg). To check you have worked out these weights correctly they must add up to 180kg, the total weight of the concrete mix (20+60+100 = 180). To answer the question, 'Does Talil have enough cement, sand and gravel to make concrete?' you need to compare the weights you worked out to the ones in the question. Although he has enough sand (85kg when he only needs 60 kg) and enough gravel (100kg and he needs 100kg) Talil does not have enough cement (he only has 15kg and he needs 20kg). Therefore, he cannot make concrete from the cement, sand and gravel he currently has.