<P> If there are 2 oranges and 3 apples, the ratio of oranges to apples is 2: 3, and the ratio of oranges to the total number of pieces of fruit is 2: 5 . These ratios can also be expressed in fraction form: there are 2 / 3 as many oranges as apples, and 2 / 5 of the pieces of fruit are oranges . If orange juice concentrate is to be diluted with water in the ratio 1: 4, then one part of concentrate is mixed with four parts of water, giving five parts total; the amount of orange juice concentrate is 1 / 4 the amount of water, while the amount of orange juice concentrate is 1 / 5 of the total liquid . In both ratios and fractions, it is important to be clear what is being compared to what, and beginners often make mistakes for this reason . </P> <P> Fractions can also be inferred from ratios with more than two entities; however, a ratio with more than two entities cannot be completely converted into a single fraction, because a fraction can only compare two quantities . A separate fraction can be used to compare the quantities of any two of the entities covered by the ratio: for example, from a ratio of 2: 3: 7 we can infer that the quantity of the second entity is 3 7 (\ displaystyle (\ tfrac (3) (7))) that of the third entity . </P> <P> If we multiply all quantities involved in a ratio by the same number, the ratio remains valid . For example, a ratio of 3: 2 is the same as 12: 8 . It is usual either to reduce terms to the lowest common denominator, or to express them in parts per hundred (percent). </P> <P> If a mixture contains substances A, B, C and D in the ratio 5: 9: 4: 2 then there are 5 parts of A for every 9 parts of B, 4 parts of C and 2 parts of D. As 5 + 9 + 4 + 2 = 20, the total mixture contains 5 / 20 of A (5 parts out of 20), 9 / 20 of B, 4 / 20 of C, and 2 / 20 of D. If we divide all numbers by the total and multiply by 100, we have converted to percentages: 25% A, 45% B, 20% C, and 10% D (equivalent to writing the ratio as 25: 45: 20: 10). </P>

What is the ratio of 2 to 7