Ask your child to guess how many of the items are in the jar and
write this number down. Remind her that her answer can be an estimate,
for example around 80. It doesn't have to be exact.
Next have your child remove a portion of the item, say in a scoop
or small cup. Talk to her about the relationship of the small amount
removed to the total. You can ask, “How many small scoops would
it take to empty the jar? How many times is the whole jar of items
compared to the amount you took out? 10 times as much? 20 times? 50
times?”
Ask your child to count how many of the item are in the portion
removed and use this information to make a new estimate. For example,
if your child guessed that the jar holds 20 times the amount removed
and the removed amount has 126 items, the new estimate is found my
multiplying 20 times 126. How does this new estimate compare to the
original one? (In making this comparison, you are highlighting how
there are tools one can use to estimate more precisely.)
Finally, ask your child to count all of the items. It is easy to
lose track when counting such a large number of things. Help her set
up a system to keep track of the counting that makes use of our place-value
system.
For example, you can take a sheet of paper and mark off 10 squares
(by drawing a line straight down the middle and 4 lines straight across).
In each square your child can count out 10 of the items until he has
filled up the entire paper with 100. Your child can count by 10’s
to confirm that there are indeed 100.
On another sheet, your child can record hundreds with other markers,
tallies, or numerals. Every time 100 is recorded, the first sheet
can be wiped clean and used again. If it looks like the number is
going higher than 1,000, your child might make groups of 10 hundreds
as well such that each larger group then equals 1,000.
Eventually, your child should have three numbers:
 | |
|
| First estimate |
| |
|
| Second, more informed estimate |
| |
|
| Actual count |
Ask your child to compare these three numbers with such questions
as:
| |
|
| How close were your estimates to the actual number? |
| |
|
| Which estimate was closer? |
| |
|
| Why do you think the estimates were different from the actual
number? |
| |
|
| Can you do anything differently to get a closer estimate
next time? |
