# Math

The heights of three plants A,B and C in a garden are in the ratio 2 : 3 :5. their mean height is 30cm
a) find the height of plant b
b) if another plant D is added to the garden and the mean height of the four plant is now 33cm , find the height of D plant

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1. the mean of 2,3,5 is 10/3
So, to have a mean height of 30, each number must be multiplied by 9, giving heights in the ratios

18:27:45

If 4 plants have a mean of 33, their sum is 4*33 = 132

18+27+45=90, so the 4th plant has height 42

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2. 2k + 3k + 5k = 3 * 30 cm

10k = 90 cm ... k = 10 cm

a) 3 * k = 30 cm

b) 90 cm + D = 4 * 33 cm ... D = 42 cm

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3. oops...

k = 9

3k = 27

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