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How do we add and subtract negative numbers?

Well, for numbers, we have a number axis which is a straight line (like this [...]) and it is divided into more pieces, of one unit each. We begin to draw this axis by placing zero in the middle (like this [...
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Answered by Maria T. • Maths tutor
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There are n sweets in a bag, 6 of which are orange, the rest are yellow. Hannah takes a random sweet from the bag and eats it, and then does so again. The probability that Hannah eats two orange sweets is 1/3. Show that n^2-n-90=0.

The probability that the first sweet Hannah eats is orange is 6/n, as there are n sweets and 6 of them are orange. If this is indeed orange, then there are now n-1 sweets left in the bag, of which 5 are oran...
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Answered by Jonny S. • Maths tutor
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What is Osmosis?

The one definition of osmosis is 'The movement of water from a high concentration to a low concentration, down it's concentration gradient, across a partially permible membrane, until osmotic pressue is equa...
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Answered by Alexandra V. • Biology tutor
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Bismuth-208, which has an atomic mass of 208u and 83 protons in the nucleus, decays through the emission of 2 alpha particles and a beta-positive particle. What isotope results from this decay?

208 83 Bi ==> x y Z + 4 2 a + 4 2 a + 0 1 B x = 208 - 8 = 200 y = 83 - 5 = 78 Proton number = 78 therefore Z = Pt Z= 200 78 Pt
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Answered by Danny L. • Physics tutor
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During the redox reaction in glycolysis, which molecule acts as the oxidising agent?

The oxidation of glyceraldehyde 3-phosphate (G3P), a three-carbon sugar, yields energy. In this oxidation, electrons and H+ are transferred to NAD+, forming NADH, and a phosphate group is attached to the oxi...
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Answered by Daniel A. • Biology tutor
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