Tips and Tricks of The Day


Record Limit : 

    2020-Feb-20
Ex: If the base of the rectangular solid is a square, and the length of the side of the base is 16 cm. and height of the solid is 20 cm .Find the volume of the rectangular solid?
(A) 2150 cm2
(B) 5210 cm2
(C) 5120 cm2
(D) 2100 cm2
Trick:
Since base of the rectangular solid is a square of side 16 cm
Area of the base= (Side)2
= (16)2
= 256 cm2
Volume of the rectangular solid = Area of the base × height 
= 256 × 20
= 5120 cm2
    2020-Feb-19
Ex: Pipe A can fill a tank in thrice the time in which pipe B can fill the same tank. If both the pipes work simultaneously, it takes 3 hours to fill the empty tank. In how many hours can A alone fill the tank? 
(A) 4 hours
(B) 6 hours
(C) 9 hours
(D) 12 hours
Trick:
Ratio between efficiency of A and B = 1: 3
Capacity of tank = 4 × 3 = 12 units
Time taken by A = 12 ÷ 1 = 12 hours
    2020-Feb-18
Ex: A candidate who gets 20% marks in an examination, fails by 30 marks. But if he gets 32% marks, he gets 42 marks more than the minimum pass marks. Find the pass percentage of marks.
(A) 52%
(B) 20%
(C) 25%
(D) 12%
Trick:
Let total mark be x.
x * (20/100)+30 = x * (32/100) - 42
0.12x = 72
x = 600
Minimum pass mark = 600 × (20/100) + 30 = 150
Minimum pass mark = (150/600) * 100 = 25%
    2020-Feb-17
Ex: A and B started a business by investing Rs. 2000 and Rs. 2800 respectively. After 8 months, A added Rs. 600 and B added Rs. 400. At the same time C joined them with Rs. 4200. Find the share of C if they get a profit of Rs.34300 after a year?
(A) Rs. 7530
(B) Rs. 7350
(C) Rs. 7300
(D) Rs. 7550
Trick:
Ratio between equivalent capitals
= (2000 × 8 + 2600 × 4) : (2800 × 8 + 3200 × 4) : 4200 × 4 
= 26400 : 35200 : 16800
= 33 : 44 : 21
Share of C = 21/(33+44+21) * 34300 = Rs.7350
    2020-Feb-14
Ex: A shopkeeper gain Rs.56 on a transistor after allowing 23% discount on its marked price. If his gain is 10%, then the marked price of the transistor is: 
(A) Rs.810
(B) Rs.800
(C) Rs.560
(D) Rs.740
Trick:
Let marked price of the transistor be Rs.100x
Selling price = Rs./रु.77x
Profit = 10%
Cost price = Rs./रु.70x
7x = 56
x = 8
Marked price = 800
    2020-Feb-13
Ex: A cuboidal tank has a length of 30 cm, a breadth of 20 cm and a height of 20 cm. The tank is placed on a horizontal table and it is three-quarters full of water. Find the area of tank which is in the contact with water.
(A) 15000 cm2
(B) 3000 cm2
(C) 2100 cm2
(D) 600 cm2
Trick:
Total area = 2(30×20 + 20×15 + 30×15)
 = 2(600 + 300 + 450) = 2700 cm.2
Required area = 2700 – 30×20
= 2700 – 30×20 = 2700 – 600
= 2100 cm.2
    2020-Feb-11
Ex: The average of five numbers is 371.8.The average of first and second number is 256.5 and the average of the fourth and fifth number is 508.Which of the following is the third number? 
(A) 360
(B) 310
(C) 330
(D) 430
Trick:
Third number = 5 × 371.8 – 2 × 256.5 – 2 × 508
= 1859 – 513 – 1016 = 1859 – 1529
= 330
    2020-Feb-10
Ex: The average age of Amit, Bablu and Chandan is 26 years. If the average age of Amit and Chandan is 29 years. What is the age of Bablu?
(A) 16 years 
(B) 18 years 
(C) 20 years 
(D) 22 years 
Trick:
Age of Bablu = Age of (Amit + Bablu + Chandan)- Age of (Amit + Chandan )
=26 × 3 - 29 × 2 
= 78 - 58 
= 20 years.
    2020-Feb-07
Ex: The edges of a cuboid are in the ratio 1: 2: 3 and its surface area is 88 cm2. The volume of the cuboid is
(A) 120
(B) 64
(C) 48
(D) 24
Trick:
Surface area of a cuboid = 2 × (l × b + b × h + h × l)
= 2 × (3x × 2x + 2x × x + x × 3x)
= 2 × (6x2 + 2x2 + 3x2) = 22x2
22x2= 88
x2 = 4
x = 2
l = 4 cm., b = 4 cm., h = 2 cm.
Volume of cuboid = l × b × h 
= 6 × 4 × 2 = 48 cm.3
    2020-Feb-06
Ex: There are 2000 students in a school. Out of these 36% are girls. The monthly fee of each boy is Rs. 480 and monthly fee of each girls is 25% less than that of a boy. What is the total monthly fee of all students?
(A). 873600 
(B). 742500 
(C). 826400 
(D). 924500 
Trick:
Number of Girls = 720
Number of Boys = 1280
Total fee = 1280 × 480 + 720 × 360
= Rs. 873600