How to do divisibility tables
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Answer:
I assume you know Arithmetic Progression .
so, we have to find the first and last 4-digit number divisible by 5
first = 1000 , last = 9990
we have a formula, = a + (n-1)d
here, is the last 4-digit number divisible by 5.
n is the number of 4-digit even numbers divisible by 5
d is the common difference between the numbers, which is 10 in this case
a is the first 4-digit number divisible by 5
9990 = 1000 + (n-1)*10
899 = n-1
n = 900
Hence, there are 900 4-digit even numbers divisible by 5
Let 
be the length of the rectangle and 
be the width. In the problem it is given that 
. It is also given that the area 
. Substituting in the length in terms of width, we have 
. Using the zero product property, 
. Solving these we get the width 
. However, it doesn't make sense for the width to be negative, so the width must be 
. From that we can tell the length 
.