What Have We Discussed ?
1.For comparing quantities of the same type, we commonly use the method of taking
2. In many situations, a more meaningful comparison between quantities is made by using division, i.e. by seeing how many times one quantity is to the other quantity. This method is known as comparison by ratio.
For example, Isha’s weight is 25 kg and her father’s weight is 75 kg. We say that Isha’s father’s weight and Isha’s weight are in the ratio
3. For comparison by ratio, the two quantities must be in the
4. The same ratio may occur in different situations.
5. Note that the ratio 3 : 2 is
Thus, the order in which quantities are taken to express their ratio is important.
6. A ratio may be treated as a fraction, thus the ratio 10 : 3 may be treated as
7. Two ratios are equivalent, if the fractions corresponding to them are equivalent. Thus, 3 : 2 is equivalent to 6 : 4 or
8. A ratio can be expressed in its lowest form. For example, ratio 50 : 15 is treated as 50/15; in its lowest form
9. Four quantities are said to be in proportion, if the ratio of the first and the second quantities is equal to the ratio of the third and the fourth quantities. Thus, 3, 10, 15, 50 are in proportion, since
10. The order of terms in the proportion is important. 3, 10, 15 and 50 are in proportion, but 3, 10, 50 and 15 are not, since 3/10 is not equal to
11. The method in which we first find the value of one unit and then the value of the required number of units is known as the
Suppose the cost of 6 cans is Rs. 210. To find the cost of 4 cans, using the unitary method, we first find the cost of 1 can. It is Rs. 210/6 (or) Rs.
From this, we find the price of 4 cans as Rs. 35 × 4 (or) Rs.