Maths: Triangles

Write these basic facts down on paper.  Remember if you are looking for the missing number you can either count on to find it or use the reverse operation and take away...

Example...

3 + ?  = 6    ......  4,5,6    the answer is 3       Reversing the sum... 6 - 3 = 3

Remember 50 has 5 tens, 90 has 9 tens...