To find the Least Common Multiple (LCM) for each pair, we can look for the smallest number that both numbers divide into evenly. Here is the step-by-step work for each problem:
1. 12 and 80
* Multiples of 80: 80, 160, 240...
* Check 240: $240 \div 12 = 20$. It works.
* LCM is
240.
2. 7 and 40
* 7 is a prime number and does not go into 40.
* Multiply them: $7 \times 40 = 280$.
* LCM is
280.
3. 25 and 35
* Both are in the 5 times table.
* $25 = 5 \times 5$
* $35 = 5 \times 7$
* LCM = $5 \times 5 \times 7 = 175$.
* LCM is
175.
4. 18 and 66
* $18 = 2 \times 9$
* $66 = 2 \times 33$
* They share a 2 and a 3 (from the 9 and 33).
* LCM = $2 \times 3 \times 3 \times 11 = 198$.
* LCM is
198.
5. 25 and 90
* $25 = 5 \times 5$
* $90 = 10 \times 9 = 2 \times 5 \times 9$
* We need two 5s, a 2, and a 9.
* $25 \times 18 = 450$ (or $90 \times 5 = 450$).
* LCM is
450.
6. 25 and 60
* $25 = 5 \times 5$
* $60 = 5 \times 12$
* We need two 5s and a 12.
* $25 \times 12 = 300$.
* LCM is
300.
7. 12 and 50
* $12 = 2 \times 6$
* $50 = 2 \times 25$
* LCM = $2 \times 6 \times 25 = 300$.
* LCM is
300.
8. 13 and 25
* 13 is prime and doesn't go into 25.
* Multiply them: $13 \times 25 = 325$.
* LCM is
325.
9. 4 and 19
* 19 is prime.
* Multiply them: $4 \times 19 = 76$.
* LCM is
76.
10. 9 and 24
* $9 = 3 \times 3$
* $24 = 3 \times 8$
* LCM = $3 \times 3 \times 8 = 72$.
* LCM is
72.
11. 20 and 55
* $20 = 5 \times 4$
* $55 = 5 \times 11$
* LCM = $5 \times 4 \times 11 = 220$.
* LCM is
220.
12. 14 and 34
* $14 = 2 \times 7$
* $34 = 2 \times 17$
* LCM = $2 \times 7 \times 17 = 238$.
* LCM is
238.
13. 16 and 82
* $16 = 2 \times 8$
* $82 = 2 \times 41$
* LCM = $2 \times 8 \times 41 = 656$.
* LCM is
656.
14. 45 and 70
* $45 = 5 \times 9$
* $70 = 5 \times 14$
* LCM = $5 \times 9 \times 14 = 630$.
* LCM is
630.
15. 24 and 18
* Multiples of 24: 24, 48, 72...
* Check 72: $72 \div 18 = 4$. It works.
* LCM is
72.
16. 48 and 54
* $48 = 6 \times 8$
* $54 = 6 \times 9$
* LCM = $6 \times 8 \times 9 = 432$.
* LCM is
432.
17. 86 and 90
* $86 = 2 \times 43$
* $90 = 2 \times 45$
* LCM = $2 \times 43 \times 45 = 3870$.
* LCM is
3870.
Final Answer:
12 and 80:
240
7 and 40:
280
25 and 35:
175
18 and 66:
198
25 and 90:
450
25 and 60:
300
12 and 50:
300
13 and 25:
325
4 and 19:
76
9 and 24:
72
20 and 55:
220
14 and 34:
238
16 and 82:
656
45 and 70:
630
24 and 18:
72
48 and 54:
432
86 and 90:
3870
Parent Tip: Review the logic above to help your child master the concept of lcm worksheet 6th grade.
