In this activity students are encouraged to solve multiplication problems by deriving from known facts, looking for groupings and skip counting. Students are encouraged to explain and share their thinking.
model multiplication facts on a one hundred array.
use the hundreds array to find groupings, known facts to solve multiplication facts
White board pen (It may also be useful for students to have a small personal copy of the grid- laminated)
Draw a rectangle on the grid. Start from the top left hand corner.
Who can tell me the fact that this rectangle is about?
Did you have to count each smile to know how many groups and what size the groups were? Why? Why not?
- How would we write this fact down?
Record the multiplication fact on the white board.
Can you work out the answer to this fact?
Can you explain how you got your answer?
Ask a range of students what the answer is and how they worked it out. Expect a range of responses.
Working out what the fact is
The fact is 7 groups of 9. You write it 7 x 9
I could see that there were 7 groups because I know that there are 5 grey smiles and 2 more. I could see that each group had 9 in it because I know that each row has 10 and there was one less.
Finding an answer
- I know the fact 7 x 9 so I knew the answer would be 63
- I knew that 7 x 10 would be 70 and so I just took off a 7 to get 63
- I knew that the shaded smiles were 25 and then I counted the groups of 10 I could see and then added the group of 8. 25, 35, 45, 55, 55+8=63
- I counted in fives and then counted on the 8 at the end 5,10,15,20,25,30,35,40,45,50,55,56,57,58,59,60,61,62,63.
- Students may need the opportunity to show their thinking with a white board pen on the grid to aid their explanation of what they did.
- Ask a range of questions. It is good to ask a couple of related facts and to encourage students to use what they have already found out.