tough sequence problems !!!!!!!!! help !

[charmaine]

1. if a sequence of 12 consecutive odd integers with increasing values has 47 as its 10th term, what is the value of its 3rd term ??

answer 33

2. on a certain test, each question after the first question is worth 50 percent less than the previous question. if the thrid question is worth 64 points. how many points is the seventh question worth ?/

answer 4

3. the population of coutry x is tripled every 10 yrs.how many yrs will it take for the population of country x to grow from 5 million to 405 million ?

answer 40

if anyone has a clue to any of these questions. help would be very much appreciated .thanks guys!!!!!

[TrizMA]

1. concsecutive odd integers mean there will be a difference of two in each term. so the difference b/w 1st and 10th term will 2*9= 18. subtract 18 from 47 so first term will be 29. 2nd term will be 31 & 3rd will be 33


2. 3rd term is 64. so keep on dividing by 2 to get next term.
4th term will be 32
5th term will be 16
6th term will be 8
7th term will be 4

or u can use difference in numbers of term i.e=7-3=4 which tells u it has to be dividided by 2*2*2*2=16. 64/16=4

3. 405/5= 81.

81= 3*3*3*3

This means u have to multiply original 5 with four 3s. Since population is tripled every 10 yrs this means it took 4*10=40 yrs

[charmaine]

hey thank u ...explanations above are great ! thanks trizma