Math Game App - Strength in Numbers (FREE for a limited time!)

There are many good math apps out there in the market. Unfortunately most of the good ones are not free. I came across the app below which I found it quite fun and useful for your primary school kids. And it is FREE! 

Strength in Numbers

Screenshots

The game play is pretty simple. Put three tiles together so that they equal to the target number on the top of the screen. In this case (refer to the picture above), the target number  is '30', so you can do '5x6'. There are also other solutions depending on the numbers given on the screen. Just remember that you need to do it as fast as you can to beat the opponent. 

It would be more fun if you compete with your child. Learning together with your child is always the best experience. Enjoy!

The importance of 'same' in Fraction questions

When it comes to fraction questions, pay attention to the 'same' word if it appears in the question. It will be the key to solve the question. Here is an example.

Question:

Adam and Bella had $5100 altogether. After Adam spent 4/5 of his money and Bella spent 5/7 of her money, they had the same amount of money left. How much money did each of them have at first?
 
Solution:

Key info: 'same amount of money left' 

Adam left 1 unit and Bella left 2 units. It means Adam's 1 unit is equal to Bella's 2 units. 

Change Adam's units to Bella's Units as shown in the table below:

17 units -> $5100
1 unit -> $300
Adam 10 units -> $3000
Bella 7 units -> $2100 

Another Question from Kiasuparents

In class 5A, there were 1/2 as many girls as boys. In class 5B , there were 1/3 as many boys as girls. The number of boys in class 5B was 2/3 as many as the number of girls in class 5A. There were 32 pupils in class 5B.

A) express the number of pupils in 5B as a fraction of the number of pupils in 5A

B) after some boys were transferred from 5A to 5B , there were 1/2 as many of 5B boys as the number of 5B girls. How many pupils were there in class 5B after the transfer ?

Solution:

5B: Boys : Girls = 1 :3 so 4units -> 32, 1unit -> 8. Boys is 8 and girls is 24
5B Boys : 5A girls = 2:3, so 5A girls is 12
5A boys: 12x2=24 
5A total pupils is 36

A) 32/36=8/9

B) After transfer
No. of 5B girls remains the same -> 24
No. of 5B boys --> half of 5B girls -> 12
Total no. of pupils in 5B -> 24 + 12 = 36

LCM Method

A question from Kiasuparents:

A group of people met at a party. Each person shook hands with everyone else. Mr Ong shook hands with 4 times as many men as women and Mrs Ong shook hands with 5 times as many men as women. How many women were there at the party ?

Solution:

Number of Coins

Another question today.

Adam has 46 10-cent, 20-cent and 50-cent coins which add up to $14.60. There were 9 10-cent coins and the rest were 20-cent coins and 50-cent coins. How many 20-cent and 50-cent coins were there?

Solution:

10-cent coins --> $0.90
so 37 coins (20-cent coins + 50-cent coins) --> $14.60 - $0.90 = $13.70

Here we use assumption method to find the answer:

Assume all 37 coins are 50-cent coin --> 37 x $0.50 = $18.50
Difference --> $18.50 - $13.70 = $4.80
Exchange --> $0.50 - $0.20 = $0.30 
Number of 20-cent coin --> $4.80 ÷ $0.30 = 16
Number of 50-cent coin --> 37 - 16 = 21

Cost, Price, Discount and Profit

Here is a question from an anonymous visitor.

At Mrs Yu's shop, there were two vases for sale at $630 each. She sold one of them at this price and earned 40% of what she paid for it. She sold the other vase later at 20% discount. If the two vases had the same cost price, how much did Mrs Yu earn altogether?

Solution:

Vase 1: 140% --> $630, so 100% --> $450 (cost price), profit --> $630-$450= $180

Vase 2: 100% --> $630, so selling price is 80% --> $504,  profit --> $504 - $450= $54

Thus, total profit is $180+$54= $234

Note:

The common mistake in this question is the misunderstanding of " earned 40% of what she paid for it ". Students often use $630 x 40% to get the earning of first vase. However, this sentence actually means "what she paid for it " (cost price) is 100%. Therefore, the selling price $630 is 140%. 

Importance of 100%

Here is another question that my students always have problem with.

Allan had 40% more money than Ben. Charles had 20% more money than Allan. When Charles spend $1680, his amount of money decreased by 50%. Allan and Ben each spent 20% of their money. How much money did three of them left altogether?

The key for this question is to let Ben be 100% and be careful with Charles' percentage.

        84% --> $1680
        1% --> $20
        Total 276% --> $5520

The common mistake is the highlighted part - finding the percentage for Charles. 

Students normally just add 20% to Allan's 140% to find Charles. But this is wrong because Allan is not 100%.

**Note: We can only add the percentage directly when the base is 100% 

Importance of reading model

My student asked me this question:

If Alex uses his money to buy 8 similar notebooks, he will still have $6 more than Bella. If Bella uses some of her money to buy the same 8 notebooks, she will have $70 less than Alex. How much is the cost of 1 notebook?

This question can be solved easily using model.

16 notebooks + $6 --> $70

16 notebooks --> $64

1 notebook --> $4

Problem sums, even complex sums, can be solved easily using model drawings.  This is so as model drawing simplifies the problem and the pictorial representation helps pupils interpret the sum in a more comprehensible manner.   

However, the use of model drawing is just one of the many other heuristic strategies used in problem solving.  We will be sharing more effective methods, taught in Singapore Schools and we improvise them, to help you better guide your child in their Math homework.