Quantitative Aptitude - Arithmetic Ability Questions

1.12.91 is the first Sunday of December 91.
So, 3.12.91 is the first Tuesday of the month.
Clearly, 10.12.91, 17.12.91, 24.12.91 and 31.12.91 are also Tuesdays.
So, 24.12.91 is the fourth Tuesday.

Let the ratio be 'R'

Total number of students = 1050

Then,

9R + 5R = 1050

14R = 1050

=> R = 75

Hence, the number of boys = 9R = 9 x 75 = 675

Choose 1 person for the single room & from the remaining choose 2 for the double room & from the remaining choose 4 people for the four person room, 

 Then, ⁷C₁ x ⁶C₂ x ⁴C₄ 

_{= 7 x 15 x 1 = 105}

Number of runs made by running = 120 - (3 x 4 + 8 x 6) = 120 - (60) = 60 

Required percentage = [(60/120)*100] % = 50%

Let the original price of rice be Rs. x

Let rice a man can buy for Rs. 500 at rs. x/kg be = R kgs

From given data, for Rs. 500

x ---- R kgs

(x + 25x/100) ---- (R - 5) kgs

=> Rx = (R - 5)(x + 25x/100)

=> Rx = (R - 5)(125x/100)

=> 100Rx = 125Rx - 625x

=> R = 25

So at rate of Rs. x/kg, man get 25 kgs for Rs. 500

=> x = 500/25 = Rs. 20

Given 2000 ---- 54 days

The provisions for 2000 men for 39 days can be completed by 'm' men for only 20 days.

i.e, 2000 ----- 39 days == m ---- 20 days

=> m x 20 = 2000 x 39

m = 3900

So total men for 20 days is 3900

=> 2000 old and 1900 new reinforcement.

Hence, reinforcement = 1900.

Passing marks are 0.6x 

so 0.3x + 30 = 0.6x   => x = 100

By mistake = x/10 

Actual value = x * 10 

% Change = 10x-x1010x×100 = 99100×100  = 99% (negative)

Since actual value is greater than the wrong value.