Ask your child to guess how many of the item 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 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 by
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 the items. It's 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, 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 she
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 one hundred 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? |
