maths mc question

2017/07/04 00:06

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maths mc question

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發問:

The sum of the 4th term and the 5th of a geometic sequence is -4.If the sum of the first two terms is 32, find the first term of the sequence.A)-6B)-0.5C)19D)64The mean mark of a mathematics test was 63 marks.Peter got 75 marks in the test and his standard score was 0.75.If Mary got 83 marks in the same... 顯示更多 The sum of the 4th term and the 5th of a geometic sequence is -4.If the sum of the first two terms is 32, find the first term of the sequence. A)-6 B)-0.5 C)19 D)64 The mean mark of a mathematics test was 63 marks.Peter got 75 marks in the test and his standard score was 0.75.If Mary got 83 marks in the same test,the her standard score would be A)0.83 B)1.25 C)2.22 D)5 同埋我想問咩叫做standard score??? THX

最佳解答:

1. let the first term be a , common ratio be r ar^3+ar^4=-4 ----(1) a+ar =32 ------(2) (1)/(2) r^3=-1/8 r=-1/2 From (2) a(1+r)=32 a(1-1/2)=32 a(1/2)=32 a=64 ______________________________________________ 2. The formula of standard score = (score - mean) / (standard deviation) 0.75 = (75-63)/(standard deviation) standard deviation = 16 standard score = (83-63)/16 = 1.25

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