1a When a number X is increased by k%,it becomes Y.But when Y is decreased by m%,it changes back to X.Express k in terms of X.
Ans:k=100m/100-m
1b Ann's weight is increased by k%.If she wants to restore her original weight,she must decrease her new weight by 15%.Using the result from (a),find the value of k correct to 1 decimal place.
Ans:17.6
Please give me steps and please help me!!!
Maths question
2007-11-11 3:19 am
回答 (1)
2007-11-11 3:53 am
✔ 最佳答案
1(a) X(1+k%) = YY(1-m%) = X
Hence X(1+k%)(1-m%) = X
(1+k/100)(1-m/100) = 1
(100+k )(100-m) = 10000
100+k = 10000/(100-m)
k = 10000/(100-m) - 100
k = [10000 - 100(100-m)] / (100 - m)
k = 100m/(100-m)
(b) By (a), m = 15
Hence k = 100(15)/(100-15) = 1500/85 = 17.647 = 17.6 (1 decimal place)
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