MENTAL ARITHMETIC

QUANTITY — UNIT — NUMBER

Lesson 1

1. Make a mental picture of a line 12 in. long

and also of a unit of measure 3 in. long. How many

times will the 3-in. unit measure the quantity 12 in.?

2.The number 4 obtained in example 1 is 4 what?

4 units of 3-in. in what?

3. This number 4 is often called the ratio of 12

in. to 3 in. What is the ratio of 12 in. to 4 in. ?

4. What part of 12 in. is equal to 3 in.? 1 is

often called the ratio of 3 in. to 12 in. What is the

ratio of 4 in. to 12 in. ?

5. Find the number of 3—in. units of length in

each of these quantities : 15 in. ; 2 ft. ; 30 in.; 1 yd.;

1 ft. 6 in. ; 2 ft. 3 in. What is the ratio of each of

these quantities to the unit? of the unit to each

quantity ?

6. In question 5 how did you find the number of

3-in. units in each quantity ?