Question

Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate (by rounding off to nearest tens): $1,08,734-47,599$

Answer 1

Step $1$: Rounding off to hundreds:

If the tens digits are $0,1,2,3$ or $4$ then round down to the previous hundred, and if the tens digits are $5,6,7,8$ or $9$ then round up to the next hundred.

Rounding off $1,08,734$ to the nearest hundreds$=1,08,700$

Rounding off $47,599$ to the nearest hundreds $=47,600$

On subtracting we get

$1,08,700-47,600=61,100$

Step $2$: Rounding off to tens:

If the ones digits are $0,1,2,3$ or $4$ then round down to the previous ten, and if the ones digits are $5,6,7,8$ or $9$ then round up to the next ten.

Rounding off $1,08,734$ to the nearest tens $=1,08,730$

Rounding off $47,599$ to the nearest tens $=47,600$

On subtracting we get

$1,08,730-47,600=61,130$

Hence, using rounding off to hundreds answer is $61,100$ and using rounding off to tens answer is$61,130$.