Quantitative Aptitude - Arithmetic Ability Questions

let speed of boat= X, speed of stream= Y
Upstream speed= X-Y
Downstream speed= X+Y
Sum of upstream & downstream= (X-Y) +(X+Y)= 2X
So, 2X= 40
X= 20 km/hr
Speed of boat : speed of stream= 600+100 :100= 7:1
So speed of Stream= 20/7 km/hr
ATQ, D/( X-Y) + D/( X+Y) = 5
D/(120/7) + D/(160/7)= 5
D= 480×5/49= 48.97 km= 50 Km(approx)

Given Dileep and Narender started a business.

Dileep invested 8000 for 12 months

Let Narender invested 'p' for 6 months

At the end of the year, their profit ratio is 1 : 1.

Hence,

8000 x 12 : p x 6

p : 16000

p/16000 = 1/1

=> p = 16,000

Hence, Narender invested amount is Rs. 16,000.

-10+10-10*10100 % = -1%

 Decrease in revenue = 1%

At least one black can be chosen in two ways from each box:
Now, probability of choosing at least one black ball from first box 

= 1/2 × [ (2C1× 2C1)/4C2 + 2C2/ 4C2 ]= 5/12

Probability of choosing at least one black ball from 2nd box
= 1/2 × [(4C1×12C1)/16C2 + 4C2/ 16C2] = 9/40

Final probability

= 5/12 + 9/40 = (50 + 27)/120 = 77/120

In the given series 1 4 9 16 22 36

1 = 1 x 1 

4 = 2 x 2

9 = 3 x 3

16 = 4 x 4

25 = 5 x 5 (Not 22)

36 = 6 x 6

Hence, the odd man in the series is 22.

Let initial quantity of milk & water in the mixture are 5x & 4x
2 litres water is added.
Hence,
New quantity of milk & water will be 5x & (4x+2)
ATQ,
5x/(4x+2) = 10/9
x/(4x+2) = 2/9 9x = 8x + 4
x=4
Hence,
New amount of water in the mixture = 4x+2 = (4*4) + 2 = 18 litres.

4b=6c⇒b=32c and 3a=4b⇒a=43b=43(32c)=2c 

a+b+c=2729 ⇒2c+32c+c=2729 ⇒c=629

 ∴a2+b2+c2=(a+b+b)2-2(ab+bc+ca) 

=(2729)2-22c×32c+32c×c+c×2c 

 =729×29-2×132 c2

= 87

Hence there are two pairs