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A staircase has n steps. You can scale the stairs by taking steps one or two at a time. How many ways are there to scale the steps?

If there are 0 steps, there is 1 possibility (you are already done).If there is 1 step, there is 1 possibility (you take one step).
If there are n steps, your first choice is either 1 step or 2 steps...

Answered by • Oxbridge Preparation tutor

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A pen is the shape of an equilateral triangle. A goat is attached to a corner of the pen on a rope. The goat eats all the grass it can reach. It can just reach the opposite fence of the pen. What percentage of the grass in the pen does the goat eat?

Step 1: Area of the penA triangle’s area is base * height / 2. Let one side (the base) have length x. By splitting the triangle in half and using Pythagoras’s rule, we get x² = (x/2)^...

Answered by Max C. • Maths tutor

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Explain how a change in an allele can stop a protein functioning correctly. (4)

If there is a change in the allele, there will be a change in base sequence of DNA (1) This means there is a change in order of amino acids (1) Therefore the protein shape changes (1) Hence, the protein m...

Answered by Lima H. • Biology tutor

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How many moles are in 50g of NaCl.

Using the formula mass=Mr * moles we can rearrange this so it equals moles= mass / Mr. We are told the mass of the NaCl is 50g however we need to work out the Mr (relative formula mass) of the NaCl too. W...

Answered by Katy H. • Chemistry tutor

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Compare and contrast facilitated diffusion and osmosis.

Facilitated diffusion is the process whereby substances are move down a concentration gradient, from a region of high concentration to a region of low concentration, using a protein as a carrier or a chan...

Answered by Sanjana C. • Biology tutor

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