Answer:
(a) 3 : 21 = 4 : 28
Explanation:
You want to know which of the following are valid proportions:
- 3:21 = 4:28
- 5:29 = 6:30
- 4:16 = 7:49
- 2:12 = 3:15
Proportion
A valid proportion is a true statement of the equality of two ratios. In general, each of the two ratios can be reduced to the same fraction in lowest terms.
3:21 = 4:28
These fractions are ...
3/21 = 1/7
4/28 = 1/7 . . . . . the proportion is valid
5:29 = 6/30
5/29 . . . cannot be reduced
6/30 = 1/5 ≠ 5/29 . . . . . not a valid proportion
4:16 = 7:49
4/16 = 1/4
7/49 = 1/7 ≠ 1/4 . . . . . not a valid proportion
2:12 = 3:15
2/12 = 1/6
3/15 = 1/5 ≠ 1/6 . . . . . not a valid proportion
The valid proportion is 3:21 = 4:28, choice A.
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