No wonder I did the 'long winded' method. I won't qualify for GEP..Nebbermind wrote:I think a similar question appeared in GEP selection test.Ender wrote:

Clever. The brighter kids would have seen it.

Basically, if you fold the four corners of the bigger square towards the centre, you will get the smaller square.

Therefore, bigger square is 2x of smaller square, ie, 288 sqcm

=> (2r)² = 288

=> r² = 288/4

Therefore pi*r² = 72pi

## Q&A - PSLE Math

### Re: Q&A - PSLE Math

- Nebbermind
- KiasuGrandMaster
**Posts:**16632**Joined:**Tue Dec 22,**Total Likes:**168

### Re: Q&A - PSLE Math

8 gwah...lulu2014 wrote:how many ways can $1.50 be exchanged with 10 cents and 20 cents coins?

Starting with 15 nos. ten cents, you can swop two ten-cents for 20-cents seven times.

- Nebbermind
- KiasuGrandMaster
**Posts:**16632**Joined:**Tue Dec 22,**Total Likes:**168

### Re: Q&A - PSLE Math

alfretztay wrote:I would solve the question as follows:EC72 wrote:

The figure below shows 2 quarter circles and a rectangle. The radius of the big quarter circle is 8 cm. The radius of the small quarter circle is 4 cm. Find the difference in area between the two shaded parts of X and Y. (Take pi as 3.14)

Observe that the area of the rectangle less that of Y is also part of the area of the big quarter.

Thus, the difference in area between the two shaded parts of X and Y -> area of big quarter - area of small quarter - area of rectangle = (3.14 x 8 x 8)/4 - (3.14 x 4 x 4)/4 - (8 x 4) =5.68sq cm

Ans :.5.68 sq cm

alfretztay

### Re: Q&A - PSLE Math

Nebbermind wrote:

Alternatively,

(i) B + C = Area of Square - Area of Bigger Qtr

(ii) A + B = Area of Rect - Area of smaller Qtr

(ii) - (i) => A - C

Nebbermind! Easier to understand this method.

- Nebbermind
- KiasuGrandMaster
**Posts:**16632**Joined:**Tue Dec 22,**Total Likes:**168

### Re: Q&A - PSLE Math

If the question means 10-cents AND 20-cents, then seven ways since All 10-cents cannot be counted.lulu2014 wrote:but 8 is the wrong ans..

### Re: Q&A - PSLE Math

Can someone help with part (b) of this question? Ans: (a)7.74cmsq (b)9.12cmsq. Thanks.