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How do I calculate a percentage increase? For example; there are 15 fish in a fish tank, after a year they have bred and now there are 20 fish in the tank. By what % has the number of fish increased?

Original value = 15 New Value = 20 Difference = New value - original value 20 - 15 = 5
(Difference / original) x 100(5/15) x 100 = 33.3%

Answered by Seyi A. • Maths tutor

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Circle with centre C, and points A,B,D and E on the circumference of the circle. BD is the diameter of the circle. Angle CDA is 18 deg and angle AED is 31 deg. Find angle EDA.

Circle theorem: angle in a semi-circle is a right angle.Therefore angle BAE = 90 + 31 = 121 degrees ABDE is a cyclic quadrilateral and:Circle theorem: Opposite angles in a cyclic quadrilateral sum to 180 ...

Answered by Jasmin H. • Maths tutor

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How do I solve a quadratic equation like x^2 - 2x - 35 = 0 without using a calculator?

If possible, you should try to factorise a quadratic. To do this, look a the factors of the constant, in this case -35. 35 is clearly divisible by 5, and 35 / 5 = 7, so 5 and 7 are one pair of factors. Th...

Answered by Alfie H. • Maths tutor

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How do I expand (x - 4)(2x + 3y)^2 ?

To start off, to make things clearer we can write the expression as:(x - 4)(2x + 3y)(2x + 3y)Now focus on just two of the brackets, say (2x + 3y)(2x + 3y). To expand this, we need to do the following four...

Answered by Hector M. • Maths tutor

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Calculate the length of PR. Give your answer correct to 3 significant figures (Diagram displayed on whiteboard)

In order to work out the unknown length of the triangle side PR, we first must identify which trigonometry equation to use. The digram gives us three values- 1 side and 2 angles. We know the hypotenuse (t...

Answered by Ali A. • Maths tutor

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