The first 3 multiples of 7 are: 7, 14, and 21.
The unit digit of 3127173 is the unit digit of 7173. The other digits of 3127 are multiples of 10 and so they cannot contribute to the unit digit. Now the unit digits of the powers of 7 are Power -- Unit digit 0 -- 1 1 -- 7 2 -- 9 3 -- 3 4 -- 1 and you are back into the loop (of 1-7-9-3). So, you only need consider 7 to the power 173 modulo 4. That is, the remainder when 173 is divided by 4. 173 = 1 mod 4 So the unit digit of 3127173 is the same as the unit digit of 7173 which is the unit digit of 71 which is 7.
All multiples of their LCM is divisible by them. lcm(8, 7, 6, 5, 4, 3, 2, 1) = 840 therefore need the largest multiple of 840 which is a 3-digit number = 840 x 1 = 840.
-5
It is a 3. Look at the ones digit of successive powers of 7; this need only be done by considering the multiplication of the ones digit of the previous power of 7 by 7 (as this is the only calculation that affects the ones digit as each successive power of 7 is the previous power multiplied by 7) and taking the result modulus 10 (to extract the new ones digit as any excess over 9 is carried into the tens column): 7¹ → 7 mod 10 = 7 7² → (7×7) mod 10 = 9 7³ → (9×7) mod 10 = 3 7⁴ → (3×7) mod 10 = 1 7⁵ → (1×7) mod 10 = 7 At this point the pattern of the ones digit will obviously repeat the sequence of the four digits {7, 9, 3, 1}. To find the ones digit of any power of 7, take that power modulus 4 use that digit from the four digit sequence. Note that when taking the number modulus 4, the result will be in the range 0-3; when the result is 0, use the 4th digit from the sequence. 2015 mod 4 = 3 → the third digit of {7, 9, 3, 1}, which is 3, will be the ones digit of 7²⁰¹⁵.
The smallest 3-digit multiple of 7 is 105 = 15*7 The largest 3-digit multiple of 7 is 994 = 142*7 So there are 142-14 = 128 3-digit multiples of 7, ie 128 3-digit numbers that are divisible by 7.
There are 13 two-digit multiples of 7.
There are 600 such numbers.
No two digit prime number exists that is a multiple of 7. All two digit numbers that are multiples of 7 are compositenumbers.
Multiples of 3 are 3, 6, 9 and so on. Multiples of 7 are 7, 14, 21 and so on. The common multiples of 3 and 7 include 21, 42, 63 and so on.
The first 3 multiples of 7 are: 7, 14, and 21.
42 is the LCM of 3, 6 and 7. All multiples of 42 are multiples of 3, 6 and 7
The unit digit of 3127173 is the unit digit of 7173. The other digits of 3127 are multiples of 10 and so they cannot contribute to the unit digit. Now the unit digits of the powers of 7 are Power -- Unit digit 0 -- 1 1 -- 7 2 -- 9 3 -- 3 4 -- 1 and you are back into the loop (of 1-7-9-3). So, you only need consider 7 to the power 173 modulo 4. That is, the remainder when 173 is divided by 4. 173 = 1 mod 4 So the unit digit of 3127173 is the same as the unit digit of 7173 which is the unit digit of 71 which is 7.
Since all 3 are prime numbers LCM = 3 * 5 * 7 = 105 All multiples of 105 are multiples of 3, 5 and 7
70 and 75
The common multiples of 3 and 7 are 21, 42, 63 and so on.
The LCM of 3 and 7 is 21