Long Jump Competition

Algebra Level 2

In a long jump qualifying competition, the average jump length of successful competitors was 6.5 meters. The average jump length of unsuccessful competitors was 4.5 meter, and average jump length of all competitors was 4.9 meters. Find the percentage (in %) of successful competitors.


The answer is 20.

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27 solutions

Gabriel Seng
Mar 17, 2014

Let a be the number of successful competitions and b be the failed competitions. Note that we are finding a/(a+b)

(6.5a+4.5b)/(a+b)=4.9

65a+45b=49a+49b

16a=4b

4a=b

a/b=1/4

a:b=1:4

So a/(a+b) = 1/(1+4) = 20%

6.5 - 4.5 = 2.0 4.9 - 4.5 = 0.4 0.4/2.0 = 0.2 = 20%

Jayson Rhoy Pael - 7 years, 2 months ago

very confusing, i took % of succesful lengths

Anany Prakhar - 7 years, 2 months ago

right approach.good

mani narayanakandar - 7 years, 2 months ago

okay it's need analyzing. very good

Nuraini Azizah - 7 years, 2 months ago

right way to get the accurate answer in less time

Ramya Mallajosyula - 7 years, 2 months ago

Very good and thank you....! :)

Siva Prasad - 7 years, 2 months ago

let x= number of successful jumper and y = number of unsuccessful jumper

then we have (6.5x + 4,5y)/(x+y) = 4.9

and we will get x = 4y

means 20%

Hazim Afifi - 7 years, 2 months ago

6.5x + 4.5y = 4.9(x+y) , x+y=100, Solve the equations and get the answer

Anay Rennie - 7 years, 2 months ago

Nice

prakash padhy - 7 years, 2 months ago
Abhimanyu Singh
Mar 24, 2014

The Very Basic Solution
Let N = Total no. of jumps
S = Total no. of successful jumps
Then, N - S = Total no. of unsuccessful jumps
According to question
Sum of all jumps = [ 4.9 × \times N ]
Sum of all successful jumps = [ 6.5 × \times S ]
Sum of all unsuccessful jumps = [ 4.5 × \times (N - S) ]
\Rightarrow [ 4.9 × \times N ] = [ 6.5 × \times S ] + [ 4.5 × \times (N - S) ]
\Rightarrow S = [ 0.2 × \times N ]
Thus 20% successful jumps.



very good

mani narayanakandar - 7 years, 2 months ago

EASIEST ONE

ALINJAR DAN - 7 years, 1 month ago

Log in to reply

Certainly.

Arghyanil Dey - 7 years, 1 month ago

v good

Aromal Ashok - 7 years, 2 months ago

very gooooooooooooooooooooooooooooooood and simple explanation

sandeep reddy - 7 years, 2 months ago

good~!!!>.<

Natsu Jett - 7 years ago

Let x = percentage of succesfull competitors.
6.5(x) + 4.5(1-x) = 4.9
Solving this equation give x = 0.2
Thus, x = 20%

This is the most elegant solution in my view. Lots of previous posters get worried about dividing by the totals. The core understanding is that the sum of [the products of length and percentage] equals the total average length.

Paul Edkins - 6 years, 11 months ago
Brahmam Meka
Mar 25, 2014

let total no of competitors be 100 successful of them be X ; unsuccessful are 100 -X ; X 6.5 +(100-X ) 4.5 =100 *4.9 ; 6.5 X -4.5 X =490-450 =40 ; 2 X =40 ; X=20 ;It is for a total of 100 persons so 20%

gud1

Himanshu Sinha - 7 years, 2 months ago
Sareang Putranto
Mar 31, 2014

suppose the successful is x and the failed is y. 6,5x + 4,5y = 4,9(x + y) 0,4y = 1,6y x/y = 1/4 so, for the successful 1/5 100 = 20% and the failed 4/5 100 = 80%

Wilbert Tumaneng
Mar 31, 2014

let x=successful y=unsuccessful ave= 4.9 4.9=(6.5x)(4.5y)/(x+y) (4.9x+4.9y)100=(6.5x+4.5y)100 (49-45)y=(65-49)x 4y=16x 1y=4x 1:4=y:x therefore %=((1/(1+4))100 =20%

Amogh Jain
Mar 31, 2014

(6.5x/100)+((4.5)*(100-x)/100)=4.9 6.5x+450-4.5x=490 2x=40 x=20

James Marinas
Mar 30, 2014

Simply (4.9-4.5=.4/(6.5-4.5)=20%

Metta Ong
Mar 26, 2014

s = sucessful; t = total

6.5s + (4.5)(t-s) = 4.9t

6.5s + 4.5t - 4.5s = 4.9t

s = (0.4/2.0)t

Manohar Mathur
Mar 21, 2014

Let number of successful=S and Unsuccessful=U. Then, distance covered by successful and unsuccessful = 6.5S+4.5U and this must be equal to 4.9(S+U) i.e., 6.5S+4.5U = 4.9S+4.9U or, 6.5S-4.9S=4.9U-4.5U or, S=(0.4/1.6)U. Let us divide both sides by (S+U). We get S/(S+U) = 0.25U/(U+S) = 0.25U/(0.25U+U)=0.25/1.25=0.2. If we multiply it by 100 for percentage, we get 20%.

my method was similar to this.explanation is lengthy.once equation is formed,by solving the equation ,gives the answer.

mani narayanakandar - 7 years, 2 months ago
Ramiel To-ong
Jan 6, 2016

nice problem

Siva Prasad
Aug 17, 2014

Thanks for all......... please reshare

Santosh Yadav
Jun 26, 2014

6.5-4.5=2 4.9-4.5=.4 .4 is 20 percent of 2

Krishna Garg
Jun 14, 2014

Let X were sucessful ,eqation becomes 6.6Xx +4.5(100-x) =100X4.9 By solving we get x =20,so successful are 20 % K.K.GARG,India

Prakash Padhy
Apr 3, 2014

20% is the answer.
6.5 x + 4.5(100-x) = 4.9 100, solving this we will get x = 20,

Moshiur Mission
Mar 31, 2014

(6.5x +4.5y)/(x + y) = 4.9 or 1.6x = 0.4y and x + y = 1 solving x = 0.2 i.e. 20%

Anzar Aznzar
Mar 29, 2014

6,5x+4,5y=4,9 , x+y=100%=1

65x+45y=49 , y = 1 - x

65x + ( 45 ( 1- x )) = 49

65x + 45 - 45x = 49

20x = 4

x = 4/20 = 1/5 = 0,2 = 20%

Don Avelino
Mar 29, 2014

6.5x+4.5y=(4.9)100, x+y=100, (x, y) = (20, 80)

Hồng Lan
Mar 28, 2014

call the percentage of success is y, we have ((6.5y+ 4.5(1-y))/1= 4.9 => 6.5y+ 4.5-4.5y=4.9 => 2y = 0.4 => y= 0.2 or 20%

Nilesh Phalke
Mar 28, 2014

X = SUCCESSFUL AND Y= UNSUCCESSFUL

6.5X + 4.5 Y = 4.9 (X+Y)

65X + 45Y = 49X+49Y

X= 1/4 Y AND X+Y = 5/4Y

100*X/(X+Y) = (Y * 1/4 )/(Y * 5/4) = 20

Parsa Karthik
Mar 28, 2014

we have average jumpers =4.5 succesful jumpers=6.5 unsuccesful jumpers=4.9

then we have 6.5/4.5=2.0 also we have 4.9/4.5=0.4 the total percentage=0.4/2.0=20%

Yodji Fufuri
Mar 27, 2014

all average of competitor is 4,9 m

x= total competitor who succesful y= total competitor who unseccesful

to solve it, (x(6,5) + y(4,5)) / (x+y) = 4,9

6,5 X + 4,5 Y = 4,9X + 4,9Y

1,6X = 0,4Y

Y = 0,4/2 * 100% = 20%

NOTE : 2 = 1,6+0,4

chal be !!!!!!!!!!!

Shubham Gupta - 7 years, 2 months ago

k(6.5)+l(4.5)=4.9 were k and l are fractions of sucessfull and unsucessfull competers then k+l=1 k(6.5)+(1-k)(4.5)=4.9 by solving we get k=0.2 percentage=0.2*100=20%

actually ,we can know the answer to this, by calculating the % increase or % drop in the ave. jump value of successful &unsuccessful players as, compared to ave. jump value of total players.......................................... like,,,, ave.value of successful players=6.5...................... (1) " " " unsuccessful players=4.5 ...............(2) and,,,,, " " " total players=4.9..............(3) now,,,, (1)-(3)=1.6 & (3)-(2)=0.4............... i.e., let 0.4 =x ,,,then 1.6 =4x .........and 5x=100%.....then x=20%

Harish Chauhan
Mar 26, 2014

let x is number of successful competitors having average jump =6.5 m and y is number unsuccessful competitor having average jump=4.5 m.

So the average jump of total competitors =4.9 m will be equal to (6.5x+4.5y)/(x+y)

which gives x/y=1/4.

So the percentage of winning competitor will be=(x/(x+y))*100 %=100/5%=20%

nice!!!!!!!!!!!

Md. Abdullah Al Masud - 7 years, 2 months ago

Let x be the number of successful competitors and y be the unsuccessful competitors. Note that we are finding x/(x+y)

(6.5x+4.5y)/(x+y)=4.9

65x+45y=49x+49y

16x=4y

4x=y

x/y=1/4

x:y=1:4

Then x/(x+y) = 1/(1+4) = 20%

Shivam Sharma
Mar 24, 2014

let x denote the succeful tries. then,

x1+x2+x3+.......+xn=6.5*(n)----------equation 1

and,let y denote the number of unsuccesful tries then, y1+y2+y3+......+ym=4.5*(m)---------equation 2

also, (x1+x2+x3+....+xn)+(y1+y2+......+ym)=4.9*(m+n)-------equation 3

now subtract the sum of equation 1 and equation2 from equation 3, we get,

m= 4 *(n)

where n are succesful total tries and m are unsuccesful total tries.

we have to find, n /(m+n)

which is equal to 20%

bit tough route, but fine!

mani narayanakandar - 7 years, 2 months ago

my solution let x % of successful jumps equation to work on 4.9 ( 100 %)= 6.5x+ 4.5(100%-x) 490%= 6.5 x +450%-4.5x 490%-450%= 2x 40 %= 2x 20%=x

rhoda cart - 7 years, 2 months ago

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