# Video

## Chain Rule: Learn Concept and Tricky Questions

In this video, we learn the concept of Chain Rule in detailed with two very important tricky questions.

[1] 40 carpenters working 8 hours a day can make 20 chairs in 60 days. After 30 days, an order of 10 more chairs came. To complete the total work on time, how many more hours per day they will have to work?

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## The incomes of A, B and C are in the ratio 7 : 9 : 12

The incomes of A, B and C are in the ratio 7 : 9 : 12 and their spending are in the ratio 8 : 9 : 15. If A saves 1/4 th of his income, then the savings of A, B and C are in the ratio of

(a) 69 : 56 : 48

(b) 47 : 74 : 99

(c) 37: 72 : 49

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## If a = 1001, b = 1002, c = 1003, then the value of a2 + b2 + c2 - ab - bc - ca is

If a = 1001, b = 1002, c = 1003, then the value of a^{2 }+ b^{2 }+ c^{2 }- ab - bc - ca is

(a) 2

(b) 3

(c) 5

(d) None of these

## If cos θ + sec θ = 2, then the value of cos^6 θ + sec^6 θ is

In this video, we covered two questions

[1] If cos θ + sec θ = 1/2, then the value of cos^{3} θ + sec^{3} θ is

(A) -1 (B) 0 (C) 1 (D) -11/8

## If A + B = 45°, then the value of (cot A -1) (cot B -1)

If A + B = 45°, then the value of (cot A -1) (cot B -1)

(a) -1

(b) 0

(c) 1

(d) 2

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## Important Concept of Profit% on Selling Price: A trader sells two articles,

A trader sells two articles, A at a 20% profit, and B at a profit of 35%. He calculates profit% on the selling price. Ratio of the profits of the both the articles is 3:4. Cost price of B is Rs. 13,000 then find the cost price of A.

(A) 15,000

(B) 18,000

## Divide Rs. 1260 among X, Y and Z so that X gets 2/9 of Y's share and Z gets 4/5 of X's share.

Divide Rs. 1260 among X, Y and Z so that X gets 2/9 of Y's share and Z gets 4/5 of X's share.

(A) Rs. 200, Rs. 800, Rs. 260

## X can build up a wall in 8 days and Y can break it in 3 days

X can build up a wall in 8 days and Y can break it in 3 days. X has worked for 4 days and then Y joined to work with X for another 2 days only. In how many days will X alone build up the remaining part of the wall?

(A) 7 1/3 days

(B) 6 days

(C) 8 days

## Discount Increase Decrease Concept with Idea generation 4 Q in 1 video

**[1]** When a discount of 20% is allowed on the marked price, the profit is 25%. If the discount is decreased to 15%, then find the profit%:

(A) 30% (B) 32.81% (C) 35% (D) None of these

## Time Speed Distance Question based on distance covered partly foot and partly bicycle

A man travelled a distance of 60 km in 10 hours. He travelled partly on foot at 4 k/h and partly on bicycle at 9 k/h. The distance travelled on foot is:

(A) 24 km