Important Question and solution: Maths

Important Question and solution:

11)      In a crowd of cows and hen, total head count is 22 and leg count is 60. Then how many cows n hen are ?

Solution: if 22 cows then leg count 22*4=88

So difference= 88-60=28

Then count of hen= 28/2=14 and cows=22-14=8

22)      A box contains 104 rs, which consist 25 p, 50 p & 1 rs in a ratio 1:4:2, then how many 25 p are there in the box.

Solution: 1:4:2= 4:14:8 … here 4+14+8=26

From above, 26rs consist number of coins of 25 p= 4

Then 112 rs consists= 4/26*104=16

33)      Present ratio of age of Trisha & Disha are 9:11, after 10 yrs it will become 7:8. What is the current age of both.

Solution:   

(77-72) X=(8*10-7*10)

       So, X=2

Then current age of Trisha = 9*2=18 and Disha = 11*2=22

44)      If rice of Type A cost as 60 rs/kg is mixed up with Type B cost as 70 rs/kg in such a way mixture cost becomes 64 rs/kg. Then tell the ratio of A and B in that mixture.

Solution:

Ratio of A & B= 6/4 = 3/2  …………………….this is allegation method

55)      In class V total 30 students and having avg weight of 40 kg while in class VIII, 20 students are having avg weight of 50 kg. what is the avg weight if we joint both the class?

Solution:

Here 0.2 is multiflying factor obtained from diff of weight (50-40)=10 divided by sum of students (30+20)=50… so it is 10/50=0.2

By this factor(0.2) we can get the value of a and b ,

So avg weight of joint class is 40+b or 50-a = 44 kg…………………….this is allegation method

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