Find the common multiples of 9 and 21 that are less than 100?
957103
9 = 3*3, and 21 = 3*7, so common multiples must have at least two factors of 3, and one factor of 7; ie they must be a multiple of 3*3*7 = 63. Theres only one - 63.\n\nOr you could just list multiples of 21: 21,42,63,84. Only one is a multiple of 9.
816611
hi,\n  regarding lcm of a set of numbers.....\n\n  the lowest common multiple (lcm) of two whole numbers\n  is the smallest whole number which is a multiple of both.\n\n  consider the numbers 12 and 15-----\n  the multiples of 12 are : 12, 24, 36, 48, 60, 72, 84, ....\n  the multiples of 15 are : 15, 30, 45, 60, 75, 90, ....\n\n  60 is a common multiple (a multiple of both 12 and 15),  \n  and there are no lower common multiples.\n\n  therefore, the lowest common multiple of 12 and 15 is \n  60.\n\n  now try it yourself for 120 and 130.
400630
Answer : 64\n\nExplanation : \n2+3=5\n5+5=10\n10+7=17\n17+9=26\n26+11=37\n37+13=50\n50+15=65\n\nSo the next number in the line should be 65, not 64.
76419
4 08 [12] 16 18 22\n6 [12] 18 24 30 36\n\nyou keep adding the number until you find the lowest one they both have.
205352
divide 68 by 4 \n17 for each space in between\n\nso,  0, 17, 34, 51, and 68
416636
the answer is 0. 5+9=14, 14x7=98 98-98=0 84x4=336, 0/336=0
388436
You could divide two of the 9's by each other to get 1, then combine the other two to get 99, then add them to get 100.
888590
Look at it like this:\n\n100 + 1 = 101\n99 + 2 = 101\n98 + 3 = 101\n97 + 4 = 101\n...\n\nSo, if you add all of the 101's up, you have 100 of them, or 100 * 101.  But you added 100 twice, 99 twice, 98 twice, ... 2 twice and 1 twice.  So, you divide by 2 to get the final answer:\n\n100 * 101 / 2 = 5050
736214
The first one is 29.16.  Divide 21.60 into 100 then multiply by 35, you get 7.56 and add that to 21.60 giving you 29.16
955059
I think it's 9*4 - (9+4) = 36 - 13 = 23.
560559
9 and 4/10\n9 and 2/5\n47/5
247655
0,1,1,5,7,11,13,13,21,23,27.......
251360
welcoming\n23 + 5 + 12 + 3 + 15 + 13 + 9 + 14 + 7 = 101
582349
2,555,555,555,550,000,000,000,000,000\nthats 2 then ten 5s then sixteen 0s
920247
There are exactly 100\n108 is the smallest and is 12*9\n999 is the largest and is 111*9\n\nTherefore there are 111 - 12 + 1 or 100 such numbers.\n(the number of numbers between a and b inclusive is a-b+1)\n\nNice try heartsensei but that wasnt your original answer.  copying others is low.
455486
20 (9,19,29,39,49,59,69,79,89,90,91,92,93,94,95,96,97,98,99)
361299
2, 9, 16, 23, 30\n\nU(n+1) = Un + 7\n\nMoving through weeks on a calendar.\n\n\n\n50, 100, 200, 400\n\nU(n+1) = 2Un\n\nDoubling ingredients in a recipe.