## Math T & W

Problem 1

Problem 2

Retrieved by International Competition and Assessment for School (ICAS) Mathematics 2009 from The University of New South Wales

A teacher wishes to store folders upright in a bookcase. Each folder is 7 cm wide. The bookcase has 3 shelves and each shelf is 1.3 m wide. How many folders can she store in the bookcase?

(A) 56 (B) 54 (C) 19 (D) 18

The picture below showed what the student think about this problem.

The student supposed two arguments to answer this question, although all arguments was described in standard method. firstly, the student try to identify idea of problem by converting the size of wide of shelf from meter to centimeter, then the student apply his mental computation by doing multiplying and dividing. Otherwise, for the second way, student still choose converting from meter to centimeter, but i can’t see multiplication used to find the answer. You see, the student directly do to divide the size that have converted by number of folder size. Actually, you may agree with the second one, since the way of thinking is logically to support what the problem wants.

Problem 3

Mathematical thinking means that think mathematically, even though many people are not having enough time to explore their reasoning to think math originally. Realistically, math is related with our daily, like an example below.

The fluctuation of exchanging value rupiah to US dollar from 18 February 2008 to 22 February 2008 was represented by following table

Date | 18/2 | 19/2 | 20/2 | 21/2 | 22/2 |

Sold value | Rp 9.091 | Rp 9.093 | Rp 9.128 | Rp 9.123 | Rp 9.129 |

Buy value | Rp 9.181 | Rp 9.185 | Rp 9.220 | Rp 9.215 | Rp 9.221 |

Can you estimate what happened the exchange value of rupiah during 19/2 and 21/2?