This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

Tuesday, August 05, 2008

Ai Tong School P5 CA2 2006 Math Q37

The average length of 2 ribbons is 2 m. One ribbon is 50 cm longer than the other. Find the ratio of the length of the shorter ribbon to that of the longer ribbon.

Solution

Shorter ----- 1 unit
Longer ----- 1 unit + 50 cm
Total Length ----- 2 units + 50 cm

Average length of 2 ribbons ----- 2 m or 200 cm
Total length of 2 ribbons ----- 200 cm x 2 = 400 cm

(Total) 2 units + 50 cm ----- 400 cm
2 units ----- 400 cm – 50 cm = 350 cm
1 unit ----- 350 cm divided by 2 = 175 cm

Shorter ribbon ----- 175 cm
Longer ribbon ----- 175 cm + 50 cm = 225 cm

Ratio
Shorter : Longer
175 : 225
7 : 9

Answer: The ratio of the shorter ribbon to that of the longer ribbon is 7:9.

2 comments:

keentolearn said...

Q) 250 pupils and some teachers attended a concert. Each teacher paid $28 for a ticket while each pupil paid $12.If the total amount paid by the teachers and pupils was $3560, how many teachers attended the concert?

Dear Mr. Song

Is the number of teachers included in the number of 250? Or are they excluded from the 250 in this case?

Excel Eduservice said...

"250" refers to pupils ONLY.

If teachers are included, it would be "250 pupils and teachers".

That said, the Q could have been clearer - "Some teachers and 250 pupils..."

Take heart. Some Science Q setters are even worse off than Maths Q setters, trying to get students/parents to understand what they ask.