model 2 find lcm of numbers Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (b)

Using Rule 4,

i.e. When a number is divided by x, y or z leaving same remainder ‘R’ in each case then that number must be K + R where k is LCM of x, y and z.

L.C.M. of 4, 6, 8, 12 and 16 = 48

∴ Required number = 48 + 2 = 50

Answer: (c)

Using Rule 5,

When a number is divided by a, b or c, leaving remainders p, q or r respectively such that the difference between divisor and remainder in each case is the same

i.e., (a – P) = (b – q) = (c – r) = t (say) then that (least) number must be in the form of (k – t),

Where k is LCM of a, b and c

Here, 12 – 5 = 7, 16 – 9 = 7

∴ Required number = (L.C.M. of 12 and 16) – 7

= 48 – 7 = 41

Answer: (b)

A makes one complete round of the circular track in $5/{5/2}$ = 2 hours,

B in $5/3$ hours and C in $5/2$ hours.

That is after 2 hours A is at the starting point, B after $5/3$ hours and C after $5/2$ hours.

Hence the required time = LCM of 2, $5/3$ and $5/2$ hours

= ${\text"LCM of " 2, 5, 5}/ {\text"HCF of " 3, 2}$

= $10/1$ = 10 hours.

Answer: (b)

Required distance = LCM of 63, 70 and 77 cm.

= 6930 cm.

Illustration :

∴ LCM = 7 × 9 × 10 × 11

= 6930