2026 · Q26
What is the greatest possible speed at which a person can walk 13.3 km and 20.9 km so that the time (in hours) required in each case is a whole number?
Elementary MathematicsHCF and LCM
- A1.7 km/h
- B1.9 km/h
- C2.1 km/h
- D2.3 km/h
Explanation
The speed must divide both distances leaving whole-hour quotients, so it is HCF(13.3,20.9)=HCF(133,209)/10. Since 133=7×19 and 209=11×19, the HCF is 19/10=1.9 km/h, option B. Taking the GCD of 133 and 209 as integers but forgetting to restore the decimal place is the usual error.