Mental Math

In math, we are using our strong base of place value to add big numbers.  This week our focus started with the objective of adding and subtracting 10.    We started modeling the concept using place value blocks.  Then we moved to more symbolic thinking using just the hundreds chart.  The students instantly noticed that on a hundreds chart 10 more and 10 less are in the columns.  We have been practicing counting by tens, but starting at different numbers.  For instance, count by tens starting at 7...7, 17, 27, 37, 47.  Below the students are putting together a hundreds chart puzzle.  They have use their knowledge of ten more and ten less to find out where to line up the pieces.  As always, the Connected Ones demonstrated terrific teamwork.

There are some excellent resources online for building number sense using the hundred's chart.   The game 100 Number Chart has the students reassembling a hundreds chart.  Also, there is Number Grid Fireworks that has the students finding particular numbers on a blank hundreds chart.  For ipad users, here are three great apps.  Mystery Number and Place Value MAB both cost $1.99 and the Counting Board chart is free.

In class, we used QR codes to practice mentally adding and subtracting ten.  We went on a QR hunt around the classroom. The QR code would give a clue like "The number is ten less than 57."  The students would record the answer, 47, then find the next code by finding the number 47.  This activity gave the students a lot of mental math practice.  Further, we used QR codes to complete a paper that practiced finding ten more and ten less of a mystery number.

The children are doing very well with these concepts.  We are moving into not only adding and subtracting 10 but also multiples of ten.  For example, students should be able to mentally solve problems like 35+20 and 67-40.  Double digit addition with regrouping (45+27) here we come!