Question

15. An alloy consists of 30% zinc, 45% nickel and the rest copper. Find the mass of copper in
400 g of alloy .
16. In a class of 38 boys, 3 were absent. 20% of the rest did not complete their homework.​

Answer 1

Answer:

15) Copper -> 100g          16) 7 boys

Step-by-step explanation:

For question 15

30/100 x 400 = mass of zinc => 120 g

45/100 x 400 = mass of nickel => 180 g

So mass of copper

=> 400 -( 120+180)

=> 400 - 300

=> 100 g

For question 16

Boys who came = 38-3 = 35

so when 20 % of the boys who didn't come:

20/100 x 35 = 7

So, 7 boys didn't complete their work .

Hope it helps !!!

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Answer 2

Answer:

hii dear,

Step-by-step explanation:

Mass of zinc = 30% of 400

= 30/100 ×400

= 120 g

Mass of Nickel = 45% of 400

= 45/100 × 400

= 180g

Mass of copper = (120+180)-400

=300 - 400

= 100 g

So the mass of Copper in the alloy was 100g

Thank u