Q1.
There are 99 numbers strictly between 700 and 800 excluding 700 and 800. How many numbers are there strictly between 7000 and 8000? Circle the correct answer: 900 999 1000
Answer
First see why 700 and 800 have 99 numbers between them.
The numbers are 701, 702, …, 799
800 – 700 = 100
Leave out both ends: 100 – 1 = 99
800 – 700 = 100
Leave out both ends: 100 – 1 = 99
Now do the same for 7000 and 8000.
The numbers are 7001, 7002, …, 7999
8000 – 7000 = 1000
1000 – 1 = 999
8000 – 7000 = 1000
1000 – 1 = 999
Circle 999.
Why it happens: from 7001 up to 7999 there is one number for every step, and there are 1000 steps from 7000 to 8000. The last step lands on 8000 itself, which we must not count.