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There are 10 boys and 20 girls in a class. The class has a test. The mean mark for all the class is 60 The mean mark for the girls is 54 Work out the mean mark for the boys.

The mean of the class is 60 for 30 students in total so to get the total marks scored by the class you need to multiply 60 by 30 which is 1800. Then you need to work out the total marks scored by the girl...

Answered by Thomas B. • Maths tutor

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What does it mean to solve an equation for x?

Answered by Jerome W. • Maths tutor

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The points {3,3,0}, {0,6,3} and {6,6,7} all lie on the same plane. Find the Cartesian equation of the plane.

A Cartesian equation is in the form ax + by + cz = d. The a, b and c constants are given by the normal vector to the plane so we must find this first. You find the two direction vectors of the plane by su...

Answered by Alejandro G. • Maths tutor

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How do I find the missing length using trigonometry?

First of all, label the sides in the right-angled triangle. Then, write out SOHCAHTOA, using three small triangles. Next, tick off the letters of the sides that either have a number, or the letter x, writ...

Answered by Patrick L. • Maths tutor

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Show that the derivative of tan(x) is sec^2(x), where sec(x) is defined as 1/cos(x). [Hint: think of tan(x) as a quotient of two related functions and apply the appropriate identity]

tan(x) is defined as sin(x)/cos(x) For a function which can be written as f(x) = u(x)/v(x) the quotient rule can be appliedThe quotient rule states f ' (x) = (u'v-v'u)/v^2 Applying this to the formula for...

Answered by Oliver C. • Maths tutor

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