We had these solutions sent in to this task, which are worth looking at carefully.
Mishika from Bal Bharati Public School, India sent in the following:
First I have joined flowers with the butterflies.
I have added 10 with 5 to make 15
Then added 10 with 6 to make 16
Then added 10 with 2 to make 12
Then added 10 with 9 to make 19
Then added 10 with 4 to make 14
Then added 10 with 1 to make 11
Last I added 10 with 7 to make 17
But I found that there is no pair for the flower 18.
Anvi from James Allen's Prep School wrote:
There are 8 flowers, all numbered between 10 and 20.
There are 16 butterflies, 8 of which are numbered 10.
First I ordered all pairs, each having a number 10 butterfly.
Next, I added the pair.
I then placed the sum of each pair on the corresponding flower.
There was no flower with number 13, hence butterflies 10 and 3 cannot go in any flower.
No pair added to 18, so there can be no butterflies on flower 18.
Macy-May from All Saints C of E Primary School wrote:
So I made all the numbers up but not 18 because there was no 8 and there was only 3 left over:
The only flower that did not have a butterfly was 18.