# Singapore Intensive Practice 4B questions..

## Recommended Posts

(US Edition)

More Challenging Problems

#9(b), pg 118

A number of tennis clubs are taking part in a competition and each club is entering two teams. Every team in the competition has to play every other team just once, except the teams from the same club do not play each other. How many games will there be altogether if 80 clubs take part in the competition?

(80x78)/2 = 3120

I need someone to talk me through this, because my non-mathy mind is having a hard time getting it, even with the answers.

********************************

# 11, pg 119

A man bought a greeting card at a shop for \$4. He paid the cashier with a \$10 bill. As the cashier did not have any small change, she went to the cashier next to her to exchange the \$10 bill for smaller bills. She then gave the man his \$6 change. Later on, the shopkeeper realized that the \$10 bill was a counterfeit. How much did the shopkeeper lose altogether?

Ds and I figured \$16; the answer in the back of the book says "the cashier lost \$6 altogether". Is this a semantics thing? We were thinking total loss to the shop, but is their answer only talking about that individual cashier? By shopkeeper, do they mean the shop or the cashier? If it's the shop as a whole, is the right answer \$16?

*********************

What I would like is an answer guide for both this and the Challenging Word Problems books that had explanations for the answers. IP has limited explanations for its word problems, but they aren't always sufficient (for me). So any of you out there looking for a book idea, I'd be interested in that!

tia for any help..

##### Share on other sites

In the first problem-

If you have 80 clubs each with 2 teams, I can subtract two from that because I don't play myself and I don't play the other team from my club. That's where 78 comes from. 80 clubs x 78 games = 6240.

Now for the dividing by two. I'm guessing that's because when I play each team, the team plays me, subtracting one from it's total. That would cut the number in half? 6240/2=3120.

Go easy on me. :001_smile: It's 7:20, and I was up 'til midnight and haven't had breakfast.

We're going to level 4 in fall. I can see I'm going to be in hot water. :001_huh:

Edited by Blessedfamily
##### Share on other sites

If they mean the whole shop this is tricky, because to me the the shopkeeper is out more than \$6. He is out the value of a card that was paid for with counterfeit money.

He now has a fake ten and no card. I mean, he gave the man \$6 real money for change-we know he's out that. He should have a \$4 increase from the sale. I guess they're thinking he isn't really out the \$4, because it wasn't subtracted out of the shopkeeper's funds.

IOW, if the cashiers had \$500 (total) in their tills before the transaction- At the end of selling a \$4 card, they should have \$504

They take the man's fake \$10 (They now have \$500 real + \$10 fake)

They give him back \$6 real money from the till. (They end with \$494 real + \$10 fake.) They are only out \$6 real money, and they have a fake ten.

\$494 + \$10 = 504, what they should have ended with, but \$10 is fake. I still say they are out \$6 + the value of the card.

Edited by Blessedfamily
##### Share on other sites

(US Edition)

.........

*********************

What I would like is an answer guide for both this and the Challenging Word Problems books that had explanations for the answers. IP has limited explanations for its word problems, but they aren't always sufficient (for me)...

:iagree:

##### Share on other sites

(US Edition)

A man bought a greeting card at a shop for \$4. He paid the cashier with a \$10 bill. As the cashier did not have any small change, she went to the cashier next to her to exchange the \$10 bill for smaller bills. She then gave the man his \$6 change. Later on, the shopkeeper realized that the \$10 bill was a counterfeit. How much did the shopkeeper lose altogether?

If it's the shop as a whole, is the right answer \$16?

I say the right answer is \$10. The \$6 given to the man as change + the \$4 they're out because he basically stole the greeting card. There isn't an extra \$6 loss I can come up with, though... but I also don't see why the book isn't counting the loss of value of the card.

I agree with the other poster on the explanation for the tennis games...

##### Share on other sites

You might also try posting to the SingaporeMath yahoo group. There are several folks there who can tell you how to solve a problem using the tools taught at that particular level. It's a great resource.

yvonne

##### Share on other sites

Thanks for everyone's responses..

I think I get #9 now, ds and I usually try to draw pictures to help us understand. We were able to get halfway there, just needed a little extra push ;)

For the second one, I think the question could have been written clearer. I was saying the store was out \$16 because they had given back \$6 in change, and they had a counterfeit \$10 that was worthless, so they'd be out \$16. But I'm not confident on that.

I've started working through the problems myself in advance, so at least I will have a clue on the tougher ones. Although there were several today where ds was getting them fine and I was the one with the problem, lol.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.