The Primary School Leaving Examination (PSLE) is an examination that 12-year-olds have to take before they proceed to their next level of education in Singapore. The results of this examination will determine the Secondary School (or more commonly known as High School in the United States of America) a child goes to. For many of the Tiger Mums and highly-competitive parents, the PSLE is everything for a child as parents believe that it will have to make or break a child's future.

The Singapore Mathematics Method

Singapore developed this method in its curriculum using a variety of models to build fundamental math skills in young children.

This method has helped Singaporean students to be ranked first in 1995, 1999, and in 2003 in the Trends International Mathematics and Science Society (TIMSS). Even with the use of technology in education, this method seemed to have helped Singaporean students trump its peers from all around the world.

Many educators all around the world (including America, Canada, and United Kingdom) have recognized this fact and have since started using the Singapore Math Method in schools. They have claimed an improvement in students' test scores.

This method that is taught in all primary schools (ages 7 to 12) in Singapore also meant that they can answer questions that even adults are unable to answer.

Tricky 'ribbon' questions

Each year, after the PSLE, eager parents will participate in online forums discussing questions in the PSLE, and a tricky mathematics question will often go viral on the internet, stumping many adults.

This year, it was the 'ribbon' question. Try your hand at it! (Do note that the phrasing of this question has been adapted)

Amy wants 200 ribbons of length 110cm for a party.

The ribbons were sold at 25 meters per roll. How many rolls will Amy need?

The most common answer found online is this:

  • Step 1 - Find the total length of ribbon required: 110 cm multiply by 200 = 22,000cm
  • Step 2 - Convert the length of one roll to centimeters: 25 m multiply by 100 = 2,500cm
  • Step 3 - Divide the total length of ribbon required (22,000cm) by the length of each roll (2,500cm) = 8.8 rolls
  • Step 4 - Round up the number as eight rolls will definitely not be enough, the answer you may get is nine rolls

Unfortunately, nine rolls is not the correct answer!

The correct answer

However, this method is erroneous as you simply cannot add up the total length of each roll and divide it by the length of ribbon required. Assuming that this is the case, it would mean you will probably have to join the ends of each roll of ribbon tape! As such, you will have to:

  • Step 1 - Divide the length of each roll (2,500 cm) by the length of each ribbon (110 cm) to find out how many ribbons can you get from one roll = 22.7 ribbons
  • Step 2 - Round down this number as 0.7 is not a full ribbon = 22 ribbons
  • Step 3 - Divide the number of ribbons required (200 ribbons) by the number of ribbons you can get from each roll = 9.09 rolls
  • Step 4 - Round up this number to ensure that Amy will have sufficient rolls = 10 rolls

Well, did you get the answer right? If not, time to hit the books!