DRDO Multi tasking staff Model paper 4

Tips & Tricks
Formula used:
LCM of fraction = LCM of numerator/HCF of denominator
Calculation:
LCM of 7, 28, 21 = 84
25/7 = (25 × 12)/(7 × 12) = 300/84
15/28 = (15 × 3)/(28 × 3) = 45/84
20/21 = (20 × 4)/(21 × 4) = 80/84
Now LCM of (300/84, 45/84, 80/84) = LCM(300,45,80)/84 = 3600/84 = 300/7