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There are 10 boys and 20 girls in a class. In a class test, the mean score of the boys is 77. The mean score of the girls is 80. What is the mean score of the whole class?

To calculate the mean of the whole class:1) Find the sum of the individual scores of the whole class. Boys: 10 x 77 = 770Girls: 20 x 80 = 1600Total of Boys and Girls: 770 + 1600 = 23702) Divide the sum of...

Answered by Anuj M. • Maths tutor

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Solve the simultaneous equations: 3x + y = -9, x^2 + 2x - 3 = y

Rearrange the first equation to equal 'y' so y = -9 - 3xSubstitute this into equation 2 so x^2 + 2x - 3 = -9 - 3xRearrange this to equal 0 so x^2 + 5x + 6 = 0Factorise this by utilising brackets so that t...

Answered by Maryum J. • Maths tutor

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Solve the following equation for x: x^2 - 4x - 17 = 4

First, take 4 from both sides of the equation to get everything on the LHS:x^2 - 4x - 17 - 4 = 4 - 4 so we have x^2 - 4x - 21 = 0We are looking to factorise the equation in the following way:(x + a)(x + b...

Answered by Jennifer H. • Maths tutor

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There are 11 pens in a box, 8 are black, 3 are red. Two pens are taken out at random without replacement. What is the probability the pens are the same colour?

For the pens to be the same colour either two black pens need to be selected OR two red pens. So start with the probability of two black pens BB: On the first selection the probability of taking a black p...

Answered by Georgia I. • Maths tutor

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b)You are given g(x) = ax + b; You are also given that g(0) = 4 and g(1) = - 6; Find the value of a and the value of b

(Question on topic of algebra taken from June 2016 OCR Past Paper)b) This question may look different to the previous one but it's still only algebra, so it;s pretty much the same. Don't let the unknows s...

Answered by Stefania R. • Maths tutor

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