### Chap 3: Estimation in Shopping...

The class is going to hold a snack party to celebrate the end of 1st Term!

Members of the class have drawn up the list of snacks for the Welfare committee to get from the supermarket (NTUC FairPrice):

1. Japanese Snacks

2. Snacks and Crackers

3. Dessert & Puddings

4. Household Items - Tissue/Wet Tissue

The Welfare committee made a quick estimation that the amount needed would be \$23.

Without using a calculator,

• How does the committee arrive at the figure?
• Do you think it's enough?
• Write down how (you think) the committee arrive at the figures
• Is that the most appropriate way to estimate for budget? Share your view.

1. The welfare committee members rounded off the figures to 1 significant figure. However, as all the figures were rounded down (All the snacks cost more than the estimated amount), \$23 is not enough to buy all the snacks.

- Christopher Nah

2. I estimated \$20. But, almost of the number I rounded down. So, I think there's a possibility that \$23 won't be enough for the snacks.

3. The money is not enough. The committee member must have rounded the prices to one significant number when he or she must round it up.

4. I do not think that the money is enough as she rounded them of to one significant number. All the balance amount of money might sum up to 3 \$

5. No,because when we estimate,we have to round it up to the highest so that when we buy the things,it will be either more or is just enough for the payment.

6. This comment has been removed by the author.

7. The actual amount needed is \$24.82
-Christopher Nah

8. The welfare committee used estimation to find out the rough gauge of the price.
It is enough as some prices e.g. \$1.24 the rounded it down, taking away those little cents but when added together costs much more.
~\$25
Zheng Jie

9. No, there will not be enough money.
I think that the committee arrive at the figure by rounding off to 1 Significant number. Since all the numbers when rounded off, it will round down.
No that is not the most appropriate way to estimate for the budget. Since all had been rounded down, they had forgotten of the few cents behind the dollars. The cents will add up to dollars, and soon there will be an excess of too much.
Another way is to round up, so that there will surely be enough money, and most probably will have some left overs.

10. I think that they must have rounded of all the item's prices to 1 significant figure, so that it will be easier to calculate the amount of money the welfare committee needs.
No they should round it off to the highest dollar so they know that they will definitely not run out of money.

11. The committee arrived at the figure by estimation. I think there will not be enough money to buy all the things as the prices are rounded off and is the exact figure is larger then the estimated figure. The committee should actually round up so that there would be extra amount of money left.

12. I think they look at the numbers and did not look at the decimal point so when they add up they would get \$23. No, I feel that that way of estimation is not the most appropriate way to estimate a budget as it would mean that the numbers that are behind the decimal point could be like a dollar or more so it would mean that \$23 would not be enough to buy all the items that the class wanted to buy.

13. \$32.50 is the real estimation. When shopping you should round up the prices not round down. Otherwise, the amount may drop drastically.

14. The committee rounded the prices to 1 significant figure. The prices were rounded down and the price is actually more than \$23 because of the cents that were rounded down. It is not the most appropriate way to estimate as the cents will be rounded down.

15. I feel that the Committee rounded all the price of the items down and calculated the total amount of money needed.

I do not think it is enough. I feel so because when the price of the items are rounded down, the value of the 1 and 2 decimal points are not included, as the value of the 1 and 2 decimal point can be added up to be a whole number it might cause the estimated price to be different.

16. No. The budget would not be enough. The number had be rounded down instead of rounding up. By rounding up, you make sure that there would be extra cash. But if you were to round down for everything, it will be sure that there would not be enough cash.

17. The committee would have rounded off all the numbers to 1(sf). However, it is not enough to buy all of them as they have lowered the amount of money. So, during shopping, we can estimate to the higher number to estimate for budget.

18. It would not be enough. They rounded it off to 1 significant figure, hence they would lose more than they earn. They only earn money from the glico pocky stick, because, when we round it to 1 significant figure, it would be rounded up, while the rest would be rounded down.

19. I think the committee arrived at the amount by rounding off the amount to the nearest dollar(some rounded up and some rounded down)
I feel that that is not the most appropriate way to estimate for a budget .In budgets,we should always round the figures up in case there is not enough money provided so they should always round the figures up,instead of rounding some of the figures down.

20. No, the amount will not be enough. The figure is just a rough estimation and the amount is not exact. They should calculate the figures from the cost itself.

21. I think the estimation is around \$25-\$30, as we need to round up each prices and do not round it down as there is a few cents left out when you round the value down and if you want to buy more stuff for the class, you can also use the remaining money to buy.

22. no the budget will not be enough they should round up all the prices to ensure that there will be enough money.

23. It would not be enough as the committee member rounded it to 1 significant number instead of rounding it up.

24. The committee rounded down the prices and so it will not be enough to buy the snacks. They must round up the prices.

25. They rounded off the prices of the items.
I think it may not be enough,as the total exact amount may be higher than that.
It is the most appropriate way to estimate for budget, as the answer gotten will be very near the exact figure.
The working (but no answer) for the exact figure is:
5.30 + (5 x 0.85) + 2.35 + (2 x 1.2) x 2 + 1.05 x 2 + 1.07 x 2 +1.24 x 2 + 1.40