Mental Math – Find The Average

To find the average number of an items between one or more groups, add the total of each group and then divide by the number of groups.

What is the average age of the people in our group?

• Sam is 4
• Rachel is 13
• Mickey is 15
• Mom is 39
• Dad is 48
• 4 + 13 + 15 + 39 + 48 = Yikes! Mental Math is hard!

Try a trick to make adding large columns of numbers easier.

• Look at the digits in the one's place (4, 3, 5, 9, 8).
• Try to find combinations that add up to 10 or 20 (4+3=7 and 7+8=15 which can be added to 5 to make 20).
• The 9 from your original array is left, so 20+9=29
• Save the 9 and bring the 2 from the ten's place to group the 3 and 4 of 39 and 48
• 2+3+4=9 Attach the 9 from the previous step and your sum is 99

The next step for finding averages is divide the sum by the total number of samples. (We added the ages of five people so 5 is our divisor.)

• 99 divided by 5! Looks like a good time for rounding. 99 round to 100 easily which is divisible by 5.
• The average of ages in this group is 20.

 

Choose some other numbers to average.

• How many buttons are you wearing?
• How many green beans are left on your plate?
• How many letters are in your name?
• Have fun making up your own categories.

Progressive Story – ABC Sentences

Take turns spinning a yarn one sentence at a time. The rules, however, require that each successive sentence starts with the next letter in the alphabet

• Player One: A freak storm blanketed the countryside with 8 feet of snow overnight.
• Player Two: Buses were cancelled and a snow day was declared.
• Player Three: Children cheered and jumped for joy.
• Player Four: Driving to work on the unplowed roads was out of the question giving parents cause to cheer as well.
• Player Five: Everyone was outside throwing snowballs and laughter filled the air.
• Can your story make it to Z?