MO C–I–1 2018

An unknown number is divisible by just four numbers from the set {6, 15, 20, 21, 70}. Determine which ones.


x = (Correct answer is: 6,15,21,70) Wrong answer

Step-by-step explanation:

6=23 15=35 20=225 21=37 70=257 LCM(6,15,20,21,70)=22357=420  a=LCM(6,15,20,21,70)=420  x1=210 x2=630 x3=1050 x4=1470 x5=1890 x6=2310 x7=2730   d(210)=1,2,3,5,6,7,10,14,15,21,30,35,42,70, d(630)=1,2,3,5,6,7,9,10,14,15,18,21,30,35,42,45,63,70,  LCM(6,15,21,70)=2357=210  k=LCM(6,15,21,70)=210  x=6,15,21,70

Did you find an error or inaccuracy? Feel free to write us. Thank you!


Tips to related online calculators
Do you want to calculate least common multiple two or more numbers?
Do you want to calculate greatest common divisor two or more numbers?

Related math problems and questions: