Madelaine88 wrote:
How many integers between 324,700 and 458,600 have tens digit 1 and units digit 3?
A. 10,300
B. 10,030
C. 1,353
D. 1,352
E. 1,339
A nice rule says:
the number of integers from x to y inclusive equals y - x + 1So, the number of integers from 324,700 to 458,600 = 458,600 - 324,700 + 1 =
133901ASIDE: We can safely round this number
133900 (you'll see why shortly)
Now let's look at how frequently we have a
1 in the tens digit and
3 in the units digit.
Integers from 1 to 100:
13 (1 integer)
Integers from 101 to 200: 1
13 (1 integer)
Integers from 201 to 300: 2
13 (1 integer)
Integers from 301 to 400: 3
13 (1 integer)
.
.
.
As we can see, for every 100 integers, there's 1 integer with a
1 in the tens digit and
3 in the units digit.
In other words, 1/100 of all integers have a
1 in the tens digit and
3 in the units digit.
So, among the
133900 integers in question 1/100 of them meet the given condition.
(1/100)(
133900) = 1339
Answer: A
Cheers,
Brent
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