Page 184 - Maths Class 06

Since, 3 : 12 = 5 : 20
Therefore, 3, 12, 5, 20 are in proportion.
(b) 10, 20, 30, 40
10 30
Ratio of 10 to 20 = = 1 : 2 Ratio of 30 to 40= = 3 : 4
20 40

Since, 10 : 20 ¹ 30 : 40
Therefore, 10, 20, 30, 40 are not in proportion.

Exercise12.2

1. Write the extremes in the following:
(a) 1 : 2 :: 3 : 6 (b) 4 : 5 :: 20 : 25 (c) 22 : 11 :: 88 : 44
(d) 5 : 7 :: 25 : 35 (e) 3 : 4 :: 6 : 8 (f) 16 : 24 :: 24 : 36

(g) 1 : 6 :: 4 : 24 (h) 50 : 150 :: 100 : 300 (i) 16 : 25 :: 32 : 50
2. Write the mean in the following:
(a) 1 : 4 :: 8 : 32 (b) 4 : 12 :: 12 : 36 (c) 25 : 5 :: 20 : 4
(d) 2 : 3 :: 24 : 36 (e) 4 : 5 :: 16 : 20 (f) 2 : 5 :: 16 : 40

(g) 25 : 30 :: 16 : 36 (h) 15 : 32 :: 135 : 288 (i) 11 : 13 :: 44 : 52
3. Which of the following are true by the rule of proportion:
(a) 1 : 2 :: 3 : 6 (b) 10 : 15 :: 20 : 25 (c) 24 : 96 :: 16 : 54
(d) 5 : 25 :: 30 : 150 (e) 75 : 150 :: 3 : 18 (f) 63 : 105 :: 18 : 30

(g) 66 : 22 :: 22 : 66 (h) 18 : 24 :: 15 : 20 (i) 114 : 222 :: 57 : 111
4. Prove that the four numbers in each of the following are in proportion:
(a) 4, 1, 8 and 2 (b) 4, 8, 16 and 32 (c) 7, 42, 5 and 30
(d) 9, 6, 15 and 10 (e) 5, 7, 25 and 35 (f) 24, 30, 12 and 15
(g) 35, 21, 10 and 6 (h) 60, 45, 40 and 30 (i) 6, 21, 18 and 63

5. Find x in the following propor tions:
(a) x : 3 :: 57 : 19 (b) 169 : x :: x : 1 (c) 80 : 32 :: x : 16
(d) 10 : 15 :: 12 : x (e) 18 : x :: 27 : 3 (f) 125 : x :: x : 5
(g) 60 : x :: 52 : 39 (h) 11 : 121 :: x : 231 (i) 121 : x :: x : 1

6. Find the fourth term of the following propor tions:
(a) 3, 9, 27 (b) 1, 10, 100 (c) 21, 27, 14 (d) 57, 76, 108
7. Find the mean propor tion between the numbers:
(a) 4, 9 (b) 4, 16 (c) 36, 16 (d) 125, 5
(e) 4, 36 (f) 25, 36 (g) 121, 100 (h) 32, 50

8. Find a number which has the same ratio to 32 as 18 has to 24.
9. If x y z, , are in proportion, find x if y = 6 and z = 12.

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