Answer: a) -32
Every number is got by multiplying the previous number by -2. Hence -32 is the answer.
Answer: c) 13
This is a Fibonacci series, where every number is obtained by adding the previous two numbers. Hence answer is 13.
Sum of seven consecutive odd numbers is 133. Find the sum of the first and third number in the series.
Since difference between any two successive odd numbers is 2, we can assume 7 consecutive odd numbers to be X-6,X-4,X-2,X,X+2,X+6. ( In our assumed series, difeerence between any two numbers is 2.)
Sum of the numbers in the series =133=X-6+X-4+x-2+x+X+2+x+4+X+6=7X
Sum of first term and last term=X-6+X+6=2X
Substituting X=19 ( which we found earlier), we can get the answer to be 2X 19=38.
Sum of six consecutive numbers that are divisible by 3 is 99. Find the sum of the first two numbers.
Answer: b) 21
Difference between successive numbers divisible by 3 will be 3. Therefore, the series takes the form as below.
Sum of all terms in the series=99=x-6+X-3+X+X+3+x+6+X+9=6X+9
Sum of firs two numbers=X-6+X-3=2X-9=2(15)-9=21
Sum of five consecutive numbers that are divisible by 5 is 275. Find the last number in the series.
Answer: a) 65
Difference between two adjacent numbers divisible by 5 is 5.
Series takes the form X-10,X-5,X,X+5,X+10
Last number in the series =X+10=55+10=65
Sum of 7 consecutive natural numbers is 91. Find the last but one number.
Answer: a) 15
Difference between two successive natural numbers is 1.
Therefore series takes the form, x-3,x-2,x-1,x,x+1,x+2,x+3
Last but one number =x+2=13+2=15
Section a of class VIII had boys and girls in the ratio of 2:1 . The current number of boys in the class is 40. Few girl students where shifted from section B to Section A. This changed the ratio of boys and girls to 2:3 Find the number of girls who got shifted from section B.
Answer: b) 40
Let the original number of boys be B and that of girls be g
It is given that B =40.
Therefore, 40G=2, Or G=20
Let the number of girls who were shifted from Section B be X. It is given that the new ratio of boys. B to the increased number of girls i.e G+Xis 2/3.
Number of players in sports namely badminton, tennis and table tennis where in the ratio of 2:3:4. Originally there were 16 badminton players. If 25% of the badminton players withdrew due to some reason, What is the new ratio of the players.
Answer: a) 3:6:8
Let the number of players in Badminton, tennis and table tennis be P,Q and R respectively.
It is given that P:Q:R =2:3:4
From the above ratio, we can easily infer that p/Q=2/3…(1) and P/R=2/4=1/2….(2)
It is given that p=16
From equation 1, P/Q=2/3 or 16/Q=2/3 . Therefore Q=16*3/2=24.
Similarly from equation. 2, P/R=1/2 or 16/R=1/2.
Let the number of badminton players present after 25% withdrew be P1.
Then p1=75% of p or 75/100*16
New ratio is p1:Q:R or 12:24:32 or 3:6:8
Let the ratio of water and milk be 1:4 in a filled can of capacity 100 litres. The mixture was added with more water so as to change the ratio of 3:8. Find the quantity of water present originally and the amount of water (in litres) added thereafter.
Answer: d) 10
Let the original quantities of water and milk be w and M respectively.
It is given that W/M=1/4….(1)
Also it is given that , total capacity of the can=W+M+100….(2)
If a fraction exists of the from a/b=c/d. Then we can very well write a/a+b=c/c+d.
Applying similar logic to equation 1 we get, W/(W+M)=1/(1+4)=1/5
But we know W+M=100
Therefore, W/100=1/5 or W=20 litres.
Substituting W=20 litres in equation 2, we get
Let X quantity of water be added so that the ratio becomes. 3/8.
But we know w=20 and M=80
Therefore, equation 3 becomes, 20+X/80=3/8
We have found W=20 litres and x=10 litres
Assume the ratio of monthly wages to team leaders and team members in a factory be 2:1. If salary of team leaders is hiked by 25 % and that of team members is hiked by 30%. What would be the new ratio.
Answer: a) 25/13
Let monthly wages of team leaders and team members be L and M respectively.
It is given that L/M=2/1
Let the hiked salary ( by 25%) of team leaders be L1.
Let the hiked salary (by 30%) of team members be M1.
New ratio L1/M1=1.25L/1.3M
But we already know L/M=2/1