Answer:
There are 15 integers between 2020 and 2400 which have four distinct digits arranged in increasing order.
Step-by-step explanation:
This can be obtained by after a simple counting of number from 2020 and 2400 as follows:
The first set of integers are:
2345, 2346, 2347, 2348, and 2349.
Therefore, there are 6 integers in first set.
The second set of integers are:
2356, 2357, 2358, and 2359.
Therefore, there are 4 integers in second set.
The third set of integers are:
2367, 2368, and 2369.
Therefore, there are 3 integers in third set.
The fourth set of integers are:
2378, and 2379.
Therefore, there are 2 integers in fourth set.
The fifth and the last set of integer is:
2389
Therefore, there is only 1 integers in fifth set.
Adding all the integers from each of the set above, we have:
Total number of integers = 6 + 4 + 3 + 2 + 1 = 15
Therefore, there are 15 integers between 2020 and 2400 which have four distinct digits arranged in increasing order.
is even if 
, and is odd if 
.
is even, since 
.
is odd, since 
.
