The ratio of family cars to the total number of cars on display in Ken's car shop was 2 : 7. ²₅ of the remaining cars on display were sports cars and the rest were saloon cars and electric cars in the ratio of 10 : 7. If there were 12 more family cars than saloon cars, how many electric cars were there?

Family Cars	Sports Cars	Saloon Cars	Electric Cars	Total Cars
2x17	5x17			7x17
	2x17	3x17		5x17
		10x3	7x3
34 u	34 u	30 u	21 u

The total number of saloon cars and electric cars is the combined repeated identity. Make the total number of saloon cars and electric cars the same. LCM of 3 and 17 is 51.

The total number of sports cars, saloon cars and electric cars is the next combined repeated identity. Make the total number of sports cars, saloon cars and electric cars the same. LCM of 5 and 5 is 85. 

Number of more family cars than saloon cars
= 34 u - 30 u
= 4 u

4 u = 12

1 u = 12 ÷ 4 = 3

Number of electric cars
= 21 u
= 21 x 3
= 63

Answer(s): 63