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Define the original cost as 100%.

So £16=85% (100-15) of the original cost.

Find 1% of the original cost by dividing both sides by 85. 

16/85=85/85%

To find the orginal cost, 1...

So we know that 3/5 teachers in the school are female, and we also know that 36 teachers are male. 

The first thing to note is that if 3/5 are female, that leaves 2/5 to be male. This is because al...

let sin(x)=u , let cos(x)=v

du/dx = cos(x),   dv/dx = -sin(x)

d[sin(x)cos(x)]/dx = v.du/dx + u.dv/dx

= cos^2(x) - sin^2(x)

The probability they wear glasses is 3/7, which means the probability they don't is 1-3/7=4/7. This means 164 students make up 4/7 of the school. To find the number that wear glasses we need to find how m...

(2+3√2, 0)  and (2-3√2, 0)