The drawing shows a stack of paper cups. The cups are 20 cm high. Each cup after the first adds 0.8 cm to the height of the stack. How many cups will fit in a dispenser that is 30 cm high?

The total number of whole cups that we can fit in the dispenser is 25

Solution:

It is given that the height of each cup is 20 cm.

But when we stack them one on top of the other, they only add a height of 0.8 to the stack.

The stack of cups has to be put in a dispenser of height 30 cm.

So we need o find out how many cups can fit in the dispenser.

Since the first cup is 20 cm high, the height cannot be reduced. So the space to fit in the remaining cups in the stack is only 30-20 cm as that's the remaining space in the dispenser

So,

30 - 20 = 10 cm

To stack the other cups we have 10 cm of height remaining

As we know that addition of each adds 0.8 cm to the stack, the total number of cups that can be fit in the dispenser can be calculated by the following equation. Let the number of cups other than the first cup be denoted by 'x'.

10 + 0.8x = 30

0.8x = 20

x = 25

The total number of cups that we can fit in dispenser is 25