Requirements: A Pack of Cards and a willing assistant.
Take 10 cards from pack including the 10 Diamonds.
Lay out card in 3 columns in a pattern of 4 down, 2 down, 4 down.
Put the 10 Diamonds at the top of the left hand column.
Group students around. You turn your head away and ask a student to point to a card.
You carry on, think allowed and then ask your assistant to point to cards asking:
Is it this one?
No.
Is it this one?
No.…………………………………………………………………………………
When your assistant points to the 10 Diamonds he will show you the position using the diamonds. The cards are laid out on the table in the pattern of the diamonds on the 10 Diamonds.
Whenever your assistant asks is it this one? You will know.
Write the word carrot inside your math text book. Do not show students.
When Mathspig was a mathspiglet we used to play this trick. It doesn’t work on everyone, but it works often enough.
Ask a student to say 15 times 15 fifteen times.
Then ask them to name a vegetable. Students say carrot 90% (I’m guessing) of the time.
To make this trick more dramatic send 10 students out of the class before you begin and tell the other half what you are about to do. Students return one at a time. How often do they say ‘carrot’? What % of students say carrot?
In every volcano disaster movie from Volcano (1997) with Tommy Lee Jones to Dante’s Peak (1997) with Pierce Brosnan someone somewhere tries to out run a lava flow.
Is this possible? (See movie cliché busted by maths here.)
Now a lava flow from Hawaii’s Kilauea volcano is threatening tiny town of Pahoa, Hawaii again. (below).
You will find excellent information about the Kilauea and other volcanoes at the
As the temperature of lava exceeds 10000 C there are very few ways to stop lava. According to the Taylor Kate Brown SMH (10 SEPT 2014) options include:
Bombing
Blasting (it with cold water)
Barricading it
Or adding concrete.
What if you are on your own.
Can you out run lava?
Lets do the maths.
Lava from Kilauea travels 17 yards per hour so the lava velocity is:
One of the greatest dangers in a volcano eruption is not the lava flow OR being hit by a lump of flying lava or rock, but by being choked by the fast moving scorching hot pyroclastic cloud.
In 1991 pyroclastic cloud blew out of the side of Mount Unzen in Japan. NASA has an excellent diagrams for such an event here.
According to the NASA website:
Highly mobile, these flows reach velocities of up to 400 kilometers (250 miles) per hour and can spread as far as 100 kilometers (60 miles) from the eruption point.
Can you out run a pyroclastic cloud?
Here is what happened in 1991 when the pyroclastic cloud blew out of the side of Mount Unzen in Japan.
This is mental maths, but not hard maths. You can play this video by 
