The total distance covered = 2 × (15 + 38 - 7×2) + 3.14 × 7 = 99.98 cm

Tks Xavier. Why 2x ( ) and why 3.14x7.

Good morning mister Tiong. I am busy now, but I will post a drawing when I can to show you why. Regards

2 (38+15) - 14 = 92 92 + (3.14 ×7) = 113.98

Tks Bak Eng. I got the same answer as you but the paper answer states 99.98 which is what Xavier Sng found.

actually come to think of it, you need to minus 7cm x4 as it covers the total diameter of 4 balls ie ball A itself and the 2 fixed balls.

So I think is this.

What about the starting 7 cm of ball A? Should that not be considered as well? This is really complex!

Interesting question

The centre of ball A must stop 7 cm from the centre of the fixed ball. After rotating half the circumference over the fixed ball, the centre of ball A must again be 7 cm away from the centre of the fixed ball.

That is how the 38 - 2×7 came about.

100%-58%=42%[50cents] so, 0.50x42=21

understand ?

Got it

Thankd

Thanks. The question is from preschooler brain teaser book. It seem quite hard to explain to him.

Pre school???? I am speechless....

Casco publisher

Since we want to form the same no, tell the child to think all the possible ways of getting 12. Then see the common no of each possible sequence. That will be the corners. Then place that no at the corners. The remainder in the middle. Do step by step.

can i know why u change it to 25:30:20

Please see the ratio and fraction in yellow. Can you accept them?

Thanks Adrian ng

Thanks Debora Prihatna