Okay i'm studying about Leading Digit Estimate....

And it has a box saying this:

**Rule for leading digit estimation:**
For each number in the calculations:

- between 1 and 10, round off to the nearest whole number;
- between 10 and 100, round off to the nearest multiple of 10; i.e. choose from 10, 20,39..... 100
- between 100 and 1000, round off to the nearest multiple of 100;
- i.e. choose from 100, 200, 300,... 1000

Then for examples they have:

(a) (= means 'approximately equal to')

23 x 317 = 20 x 300

= 6000

then in small bold writing, it has in brackets (applying the rule 2x3, then add the zeroes)

then:

(b) 4250 divided by 23 = 4000 divided by 20

= 400 divided by 2

= 200

then in small bold writing it has in brackets (cancel tens)

Can you

**please** explain, i haven't got a clue... :confused: