1. an alloy contains zinc and copper in the ratio of 7:9 find weight of copper of it had 31.5 kgs of zinc. 2. compare the following ratios

i) 2:3 and 4:5
ii) 11:19 and 19:21
iii) ½ : ⅓ and ⅓ : ¼
iv ) 1⅕ : 1⅓ and ⅖ : 3/2

v) if a : b = 6:5 and b:c = 10:9, find a:c

vi) if x : y = ⅙:⅛ and y : z = ⅛: ⅒, find X : z

sorry many questions

Step-by-step explanation:

Question (1). An alloy contains zinc and copper in the ratio of 7 : 9.

If the weight of an alloy = x kgs

Then weight of copper =

                                      =

And the weight of zinc =

                                      =

If the weight of zinc = 31.5 kg

31.5 =

x =

x = 72 kgs

Therefore, weight of copper =

                                               = 40.5 kgs

2). i). 2 : 3 =

        4 : 5 =

Now we will equalize the denominators of each fraction to compare the ratios.

=

Since,

Therefore, 4 : 5 > 2 : 3

ii). 11 : 19 =

    19 : 21 =

By equalizing denominators of the given fractions,

And

Since,

Therefore, 19 : 21 > 11 : 19

iii).

              =

Now we equalize the denominators of the fractions,

And

Since

Therefore, will be the answer.

IV).

Similarly,

By equalizing the denominators,

Similarly,

Since

Therefore,

V). If a : b = 6 : 5

  And b : c = 10 : 9

 Since a : b = 12 : 10

 And b : c = 10 : 9

 Since b = 10 is common in both the ratios,

 Therefore, combined form of the ratios will be,

 a : b : c = 12 : 10 : 9

4 and 5)16.97 or 12√2

6)15.59 or 9√3

7)y = 15.59 or 9√3     x =27

8)17.80