Answer:
Explanation:
We could start by listing multiples of 4 and looking for patterns. Do
you know what a multiple of a number is? It's that number multiplied
by another number. So the first multiple of 4 is 4x1, the second
multiple of 4 is 4x2=8, the third multiple of 4 is 4x3=12, etc.
Let's make a table of multiples of 4 from 1 to 100, with columns A-E
across the top and rows 1-5 down the left-hand side:
A B C D E
1 4 8 12 16 20
2 24 28 32 36 40
3 44 48 52 56 60
4 64 68 72 76 80
5 84 88 92 96 100
Now let's look at these multiples, remembering that there will be nine
more tables like this one from 101-1000.
Let's look for 6,7,8,9, and 0 in the columns first. Aha! We can erase
all of columns B, D, and E because there's a 6 or an 8 or a 0 in each
number in those columns. Now we're left with just:
A C
1 4 12
2 24 32
3 44 52
4 64 72
5 84 92
Now let's look at the rows. Wow! We can eliminate rows 4 and 5 because
they have 6, 7, 8, or 9, leaving:
A C
1 4 12
2 24 32
3 44 52
Just 6 numbers left!
So if from 1-100 there are 6 multiples of four that do not contain any
of the digits 6, 7, 8, 9, or 0, how many multiples of four like this
are there from 1-1000?