Look at this series: 80, 10, 70, 15, 60, ... What number should come next?
a)20
b)25
c)30
d)50

• ans= 20
  consider the alternate terms
  80 70 60 ... its in decreasing order of 10 .
  and 10 15 ....... its in increasing order of 5 . so next ter m will be 20
  
• 13 years agoHelpfull: Yes(6) No(1)
• 20.
  series is like (n-10),(m+10). where n starts from 80 and m starts from 10.
• 13 years agoHelpfull: Yes(3) No(0)
• the difference between 1st and 3rd no=10
  3rd and 5th no=10
  the difference between 2nd and 4th no=5
  difference between 4th and 6th no=5
  therefore the number should come next is 20
• 13 years agoHelpfull: Yes(2) No(1)
• the 2nd digit is 10
  and the fourth digit is 15 i.e., 10+5
  hence the sixth digit will be 15+5=20
• 9 years agoHelpfull: Yes(1) No(0)
• ans is 20
  as there are two series
  1st one : 80 70 60 (60-10)=50 and
  2nd one :10 10+5=15 15+5=20
• 7 years agoHelpfull: Yes(1) No(0)
• 20 sequence alternate
• 9 years agoHelpfull: Yes(0) No(0)
• 80-10
  70-15..so odd position decreasing by 10 & even increasing by 5..A)20
• 9 years agoHelpfull: Yes(0) No(0)
• Answer : 20
  
  80 10 70 15 60
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  These series is decreasing by 10 in every alternative step.
  and where as second alternative series is increased by 5 in every step
  i.e..,10 15 20
  
• 9 years agoHelpfull: Yes(0) No(0)
• 20 because the betwewen the odd positoned no. is 5
• 9 years agoHelpfull: Yes(0) No(0)
• 20
  In this two series are there
  80,70,60 diff is 10
  10,15 the diff is 5 so next number should be 20
• 7 years agoHelpfull: Yes(0) No(0)
• 20
  odd positions are decreasing by 10 and even positions are are increased by 5
• 4 years agoHelpfull: Yes(0) No(0)
• 20 is the answer
  
  80, 70, 60 are pattern with difference of -10
  10, 15, 20 are pattern with difference of +5
• 4 years agoHelpfull: Yes(0) No(0)