Sunday, May 31, 2015

June 3 on Donuts

Donuts costs P42 each. Half a dozen cost P252. A dozen cost 380 and two dozens cost 595.

Describe strategies that allow us to estimate the cost per donut easily.

Thursday, May 28, 2015

June 2 on Cafe

Marcus buys 3 cups of hot beverages and they cost $5.10 .

All the beverages are different.

What hot beverages did he buy? How many possible answers are there?

Other than guess and check, students can use reasoning to solve this problem. They are required to use their knowledge about number properties to help them reason.

May 31 on Reservoirs

Soil samples will be taken from reservoir beds, at 0.9m, 1.9m, 2.9m below the bed, and if possible, at every 3m, up to a depth of about 30m | Straits Times

June 1 on Torch Bearers

Charles is 83 years old. Jesy turns 9 years old on the day of the parade. 

They are the oldest and youngest torch bearers at SEA Games Torch Parade.

How much older is Charles than Jesy?

May 30 on Big Numbers

Big numbers are not so common.

But in today's newspaper, I come across several. Parents can use the newspaper as a source of guiding their children in learning mathematics.

In 1974, anthropologists in Ethiopia found the astonishing fossilised remains of a human-like creature who last walked the planet some 3.2 million years ago. | Straits Times

The above can lead to an understanding of the magnitude of the million. The fact that this year is just 2015 years after the birth of Christ makes 3.2 million years ago seems like several lifetime (literally!!) away.

Did you know that Singapore does quite a bit of business in exporting ornamental fish?

Value of Ornamental Fish Exported
2008 USD69 million
2009 USD60 million
2012 USD62 million
2013 USD56 million

Parents can use this with upper primary children to calculate percentage change. Or learn the use of line graphs to make predictions.

Wednesday, May 27, 2015

May 29 on Drinks

For every banana used, how many of each fruit are needed?

For example, we would need 6 fourths mangoes. That's 1.5 mangoes - so we need 2 mangoes and have half left over. 

May 28 on Market Place

Tomatoes are sold at 12 cents per 100g.

Sweet potatoes are sold at 35 cents per 100g.

Oranges cost $4.50 for 5.

Cucumbers 60 cents each or $1 for two.

May 23 on Sea Creatures

Lugworms are rarely seen but they leave these on beaches at lowtide. You have to dig them out if you are curious or if you want to use them as a bait.

What measurements are needed to find the volume of this coil structure created by the lugworm. 

Thursday, May 21, 2015

May 19 on Transportation

Heathrow Express left Paddington at 0941 and arrived at the airport at 0955. Even with 13 minutes walking time to the check-in counters I was early for my 1030 checkin. What is the latest Heathrow Express I could take to be not late for my 1030 checkin? 

By 1020 I was through security screening. But it is another 15-minute walk to the gate. Boarding is at 1130. What is the latest time my Heathrow Express should leave Paddington for me to be at the boarding gate at 1130.

Sunday, May 17, 2015

May 18 on Markets

How much does 4lbs of tomatoes cost?

Note to Parents | The ability to compute on paper is less important than the ability to use mental strategies such as doubling to arrive at an answer. Or the ability to tell how much change is expected if one pays £5. 

Also how many tomatoes make a pound, approximately? 

Saturday, May 16, 2015

May 17 on Flights

The number of flights taking off from Sunavarbhumi Airport are as follows 0800-0859 14 flights
0900-0959 19 flights
1000-1059 19 flights
1100-1159 16 flightA

On average, how many flights depart from Sunavarbhumi Airport per hour? 

What if the data is  

0800-0859 14 flights
0900-0959 19 flights
1100-1159 19 flights

Does the answer change? 

May 16 on Trains

The Heathrow Express is the best way to and from the airport. It costs £21.59 one-way except on Saturday when it costs only £10 one-way. 

You can also buy a two-way ticket. 

How much should a two-way ticket cost so that it is never more expensive to use it? 

Thinking versus computation - it is important to engage your child in conversation about how much a two-way ticket might cost. Should it be twice of £21.90 (mentally, 20p less than £44)? It is usually cheaper than that to encourage passengers to buy two-way tickets. 

The key to help your child is to have conversation and discussion. You are not helping very much by simply putting a stack of worksheets in front of the kid. 

Sunday, May 10, 2015

May 10 on Signs

The ability to see basic shapes in composite shape is a fundamental ability called visualization. 

L can be seen as made up of two rectangles. How about N and K?

Saturday, May 2, 2015

May 2 on Penang Street Food

The regular plate cost RM2.80 and the premium plate, fried with duck eggs, cost RM3.50. In 15 minutes, the hawker sold RM32.90. Is that possible?

Note for Parents
Students who are strong in maths have good number sense. They can reason if 2.80m + 3.50n = 32.90 is possible.

Some may reason that since 2.80 + 3.50 = 6.30, there is some chance of getting the 0.90 in 32.90. So is it possible?

Also students with good measurement sense can tell if it is reasonable to prepare 10 plates of the dish in 15 minutes is reasonable. You need knowledge of context in this case. This is also an example of linking mathematics to everyday situations.

Photo | Street Food in Penang