008. Rounding and Estimation Strategies

Learning Intentions

To understand that in some practical situations, an estimate or approximation is accurate enough
round numbers to a degree of accuracy (e.g. to the nearest 100)
estimate numerical answers to arithmetic questions by rounding each number in the question

Understanding place value (ones, tens, hundreds, thousands)
Knowing how to compare digits to midpoint values (e.g. $5$ in tens, $50$ in hundreds)
Understanding that rounding changes a number to a nearby value
Familiarity with basic arithmetic operations
Ability to perform addition, subtraction, multiplication and division

Decide if an estimate is sufficient:

a) A school has $1 982$ students. About how many students is this?
b) A truck carries $9 745$ kg. Is $10 000$ kg a reasonable estimate?

Round to the nearest value:

a) $368$ to the nearest $10$
b) $4 257$ to the nearest $100$
c) $12 640$ to the nearest $1 000$

Round to the nearest $100$ :

a) $243$
b) $1 764$
c) $8 451$

Estimate by rounding each number:

a) $487 + 213$
b) $1 596 - 742$

Estimate by rounding each number:

a) $49 \times 18$
b) $1 238 \div 6$

a) A town has $3 976$ people. About how many people is this?
b) Is $4 000$ a reasonable estimate?

Round to the nearest value:

a) $452$ to the nearest $10$
b) $6 384$ to the nearest $100$
c) $27 540$ to the nearest $1 000$

Round to the nearest $100$ :

a) $376$
b) $2 549$
c) $7 851$

Estimate by rounding each number:

a) $612 + 388$
b) $2 183 - 905$

Estimate by rounding each number:

a) $52 \times 21$
b) $1 457 \div 7$

Round to the nearest $10$ :
a) $64$
b) $178$
c) $905$
Round to the nearest $100$ :
a) $245$
b) $1 732$
c) $6 451$
Round to the nearest $1 000$ :
a) $3 684$
b) $8 249$
c) $15 620$
Estimate by rounding each number:
a) $398 + 601$
b) $2 482 + 519$
c) $1 706 + 2 295$
Estimate by rounding each number:
a) $802 - 389$
b) $3 195 - 1 102$
c) $5 640 - 2 318$
Estimate by rounding each number:
a) $47 \times 19$
b) $62 \times 28$
c) $205 \times 4$

Explain why $349$ rounds to $300$ to the nearest $100$ .
A student rounds $2 650$ to $2 600$ to the nearest $100$ . Explain the error.
Which is the better estimate for $598 + 204$ :
a) $600 + 200$
b) $590 + 210$
Explain.
Why is estimation useful before solving a problem exactly?

A factory made $4 812$ toys. About how many toys is this to the nearest $1 000$ ?
A shop sold $398$ items on Monday and $607$ on Tuesday. Estimate the total.
A school budget is $9 845$ dollars. Estimate to the nearest $1 000$ .
A bus travels $52$ km per trip for $21$ trips. Estimate the distance.
A warehouse stores $3 642$ boxes across $8$ rows. Estimate how many per row.