Video Transcript
Olivia and Victoria are making a
robot out of blue and yellow blocks. Olivia has counted out 19 blue
blocks. Victoria says they have 39 blocks
in total. How many yellow blocks do they
have?
We know that Olivia and Victoria
have 39 blocks in total. We know that Olivia has counted out
19 blue blocks. We need to work out how many of the
blocks are yellow. To solve this problem, we need to
take apart or subtract. If we subtract 19, which is the
number of blue blocks, from 39, which is the total number of blocks, that will tell
us how many of the blocks are yellow. So we need to calculate 39 take
away 19. We could find the answer quickly
using column subtraction. The number 39 has nine ones, and
the number 19 has nine ones. So we have nine ones, and we need
to take away nine ones. Nine take away nine is zero.
Now we can just subtract the
tens. 39 has three 10s. 19 has one 10. We know that three take away one is
two, so three 10s take away one 10 leaves us with two 10s. 39 subtract 19 equals 20. We can check our subtraction
calculation using addition. We know that there are 19 blue
blocks and 20 yellow. Does 19 plus 20 equal 39? Nine ones plus zero ones is
nine. One 10 and two more 10s gives us a
total of three 10s. 19 plus 20 is 39. We were correct. Victoria and Olivia have 39 blocks
in total. If 19 of the blocks are blue, then
20 are yellow. 39 subtract 19 equals 20. Olivia and Victoria had 20 yellow
blocks.
