number systems Model Questions & Answers, Practice Test for ssc chsl tier 1

Answer: (a)

LCM of $2/3, 4/9, 5/6$

${\text"LCM of " (2,4,5)}/{\text"HCF of" (3,9,6)} = 20/3$

Answer: (b)

LCM of the numbers = 420.

Hence there must be (420 × 2) + 2 = 842 beads.

Answer: (a)

1 + 2 + 3 + ..... + 40 = ${40 × 41}/2 = 820$

Since at each time any two numbers a and b are erased and a single new number (a + b – 1) is writen.

Hence, each one is subtracted and this process is repeated 39 times.

Therefore, number left on the board at the end = 820 – 39 = 781.

Answer: (b)

For number between 600 to 700 :

Number of 6 at the units place = 10

Number of 6 at the tens place = 10

Number of 6 at the hundredth place = 100

For number between 501 to 599 :

Number of 6 at the units place = 10

Number of 6 at the tens place = 10

Hence, total number of 6 between (501 – 700)

= 10 + 10 + 100 + 10 + 10 = 140

Answer: (d)

Let the three prime numbers be x, y, y + 36

x + y + y + 36 = 100 ⇒ x + 2y = 64

2y is an even number always

We know that

Even + even = even or odd + odd = even

So x has to be even to satisfy x + 2y = 64

The only even prime on is 2

Put x = 2 ⇒ 2y = 62 ⇒ Or y = 31

So the numbers are 2, 31, 67