Predictions

Dear writers of elementary math problems: If you ask children to “predict how many heads and tails you will get if you flip a coin 10 times,” there is no single correct answer since even a prediction of 10 consecutive heads is valid (if not the best). Please use some other verb besides “predict.” Thank you.

25 divided by 5 is 14

Teaching base 10

Price (on the day of this writing) on Amazon.com for a base-10 starter kit, featuring 100 small plastic blocks, 30 rods (representing 10), 10 plates (for 100), and one big cube (for 1000): $31.32.

Cash value of 100 pennies, 30 dimes, 10 dollar coins, and a $10 bill: $24.00.

Analog clocks

What time is it?

From the perspective of an elementary student — even a good student who generally can read the hands of a clock correctly — the answer probably is 2:50. After all, the hour hand is pointing much closer to the 2 than to the 1.

To address this misconception, perhaps the best suggestion that I’ve heard is using the analogy of waiting for your birthday. A child doesn’t turn 7 until his (or her) birthday comes. On the day before his birthday, he still has to say that he’s 6. Likewise, if the minute hand is just a few minutes before 7:00 and the hour hand is not all the way at seven, we still have to say that the time is six-something.