## Ho Soo Thong   Ho Shuyuan

This write-up illustrates the bar modelling approach to a variant of a recently highlighted 2017 PSLE question. The problem solving strategy involves the use of Euclidean Division Algorithm to depict the two “remainder” situations.

## A Ribbon Problem

Jane, a sales supervisor, has to prepare 150 ribbons for gift wrapping. Each ribbon is of length 160 cm. The ribbons are cut out from tapes of length 20 m each.
How many tapes are needed to prepare all 150 ribbons?

Solution
For the number of ribbon that can be made from each tape of length 20 m = 2000 cm,we construct a bar model with Euclidean Division Algorithm.

12 ribbons can be made per tape and the remaining 80 cm of tape has to be discarded.

For 150 ribbons, we again apply the Euclidean Division Algorithm and the bar model shows that one more tape is needed for the remaining 6 ribbons.

Therefore, Jane needs 12 + 1 = 13 tapes.

Remarks
An earlier PSLE question (15/02/2014 ) also involves a non-discarded “leftover“ situation. This was solved with bar model and Euclidean Division Algorithm. This also highlight the use for a pictorial view of the problem to give students a clearer understanding of the situation described in the problem.