Hi, thanks for the challenge

No. 6:

If the original no. is n.

Shifting the decimal point 2 places to the right means it's multiplied by 100.

thus, the difference is 100n - n = 99n = 544.5

So, n = 544.5 / 99 = 5.5

Ans: The original no. is 5.5.

No. 17:

When 4 marbles cause a rise of 8 cm, it means one marble causes a rise of 2 cm.

So, when 1 marble is removed, there will be a drop of 2 cm, resulting in the water level to be (10 + 6) = 16 cm

The metal block causes the water level to rise to 22 cm.

It means the metal block causes a rise of (22 - 16) = 6 cm

a) Since it is the same tank that is used, the base area is constant, and the volume is proportional to the 'height' of water.

Thus, the ratio of the volume of 1 marble to volume of metal block is 2 cm : 6 cm = 1:3.

b) Volume of metal block - volume of 2 marbles

= 450 cm^2 (6 cm - 2 x 2 cm)

= 450 cm^2 x 2 cm

= 900 cm^3