The first Noel

Algebra Level 1

On a cold winter’s night that was so deep, the poor shepherds lay huddled amongst their sheep. If there were 100 heads and 300 legs in the field, how many sheep did the shepherds have?

The First Noel The first Noel the angles did say
Was to certain poor shepherds in fields as they lay
In fields where they lay keeping their sheep
On a cold winter’s night that was so deep.

Details and assumptions

A sheep has 4 legs, a shepherd has 2 legs.


The answer is 50.

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22 solutions

Let's take the number of shepherds as x x and the number of sheeps as y y . We know that shepherd's and sheep's have 1 1 head each. So, we can get an equation, x + y = 100 ( 1 ) x+y=100----(1) But, a shepherd has 2 2 legs whereas a sheep has 4 4 legs. Hence, we get another equation, 2 x + 4 y = 300 ( 2 ) 2x+4y=300----(2) Multiplying equation ( 1 ) (1) with 2 2 and subtracting it from equation ( 2 ) (2) , we get 2 y = 100 2y=100 y = 50 \Rightarrow y=50 As the number of sheep is y y , the answer is 50 \boxed{50} .

Nice solution soham !!

Devesh Rai - 7 years, 5 months ago

Thanks Devesh.

Soham Dibyachintan - 7 years, 5 months ago

Nice illustration. @ Soham

Bijoy Rana - 7 years, 5 months ago

Thanks Bijoy.

Soham Dibyachintan - 7 years, 5 months ago

what about the other heads and legs?????

Fahim Bakhtier - 7 years, 5 months ago

About whch heads and legs are you talking?

Soham Dibyachintan - 7 years, 5 months ago

yeah but.... there are 100 heads so 100 animals no?

Marco Froelich - 7 years, 3 months ago

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they said 100 heads not 100 heads of 100 animals so there was 50 humans and 50 animals

Rajnish Kaushik - 7 years, 1 month ago
Sourav Maji
Dec 19, 2013

x=no. of shepherds y=no. of sheep,

x+y=100( for heads) 2x+4y=300(for legs)

solving ,we get x=50,y=50

Sayantan Guha
Dec 18, 2013

Let there be X sheep & Y shepherds. Each sheep has 4 legs & each shepherd has 2 legs. According to the given data: X + Y = 100..........................(i) 4X + 2Y = 300...........................(ii) Solving (i) & (ii) we get X = Y = 50

This problem can be solved easily using algebra to construct the simultaneous equations:

x + y = 100 x + y = 100

4 x + 2 y = 300 4x + 2y = 300

However, I won't solve those. I want to share another approach for this type of problem, which I learnt when I was in primary school, roughly translated as "Temporary Assumption".

Assume for a moment that all 100 heads belong to the sheep. With this assumption, the number of legs must be 400. This exceeds the number of legs given, which is 300.

Now, if we replace 1 sheep by 1 shepherd, the number of legs decreases by: 4 2 = 2 4 - 2 = 2 . If we replace 2 sheep by 2 shepherds, the number of legs decreases by 4 and so on. We must continue to replace sheep by shepherds until the total legs reach the given number.

The number of sheep must be replaced by shepherds, a.k.a. the number of shepherds is:

400 300 4 2 = 50 \frac{400-300}{4-2} = 50

Hence the number of sheep is:

100 50 = 50 100 - 50 = 50

Shivam Khosla
Dec 19, 2013

Let x be the number of sheep and y be the number of shepherds.....then total heads=heads of x sheeps + heads of y shepherds....derfor x+y=100...x sheeps will have 4x legs and y shepherd will have 2y legs derfore total legs=300=4x+2y slving equations we get x=50

perfect

Jahir Shimanth - 7 years, 5 months ago
Ajay Maity
Dec 18, 2013

Let the number of sheep be denoted by S and the number of shepherds be denoted by H.

Since there are total 100 heads in the field, we have S + H = 100 ....... (1)

Since there are total 300 legs in the field, and since each shepherd has 2 legs and each sheep has 4 legs, we have 4S + 2H = 300 ...... (2)

Solve equations (1) and (2), we get S = 50.

That's the answer!

But how ??? youve get 50 ?

Jhay-ar CLink'z - 7 years, 5 months ago

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Step-by-step solution:

We have two equations:

S + H = 100 .... (1)

4S + 2H = 300 ..... (2)

Two equations, two unknown. Solve it using simultaneous equations method.

Multiply equation (1) by 2,

2S + 2H = 200 ..... (3)

Now, subtract (3) from (2),

2S = 100

S = 50

I hope you got it now!

Ajay Maity - 7 years, 5 months ago
Tom Zhou
Dec 18, 2013

Let us assume that all 100 100 heads belong to shepherds. Then there are 100 × 2 = 200 100\times2=200 legs, which is 300 200 = 100 300-200=100 less than the actual amount. For each shepherd that we switch to sheep, there is a gain of 4 2 = 2 4-2=2 legs. We need a gain 100 100 legs so we need to switch 100 ÷ 2 = 50 100\div2=\boxed{50} shepherds to sheep.

Fatima Fouad
Apr 30, 2014

The number of total legs is 300, while the heads are only 100. Assume the number of shepherds to be x. This makes the number of sheep (100-x). Hence, 2x+4(100-x)=300. Solve the equation to get the correct answer of 50. This is the number of shepherds, subtracted from 100, we get the number of sheeps, which in this case, are also 50.

Shaza Rae
Jan 5, 2014

Lets say the number of sheep is represented by "X" and shepherds by "Y".

Each shepherd and sheep has 1 head each, therefore:

X + Y = 100

If one sheep has 4 legs, and 1 shepherd has 2 legs,then

4X + 2Y = 300

This is because the NUMBER of shepherds and sheep are represented by "X" and "Y" respectively.

Substitute: X + Y = 100 into 4X + 2Y =300 X = 100 - Y

4(100 - Y) + 2Y =300 400 - 4Y + 2Y = 300 -2Y = - 100 Y = 50 Remember that each shepherd and sheep has 1 head each. So if Y = 50, therefore X = 50

Srikrishna Raghu
Dec 25, 2013

Let x be a part of a sheep's body and y be a part of a shepard's body. Taking x and y's heads, x + y = 100. Taking x and y's legs, 4x + 2y = 300. By using elimination method, multiply the first equation by 4. So, 4X + 4Y = 400 subtract,4x + 2y =300 So, 2y = 100 Therefore, y= 50. x=100-50 = 50. Therefore the shepards have 50 sheep.

count legs of shepherds = \frac{2}{6} \times 300 = 100 count head of shepherds = \frac{100}{2} = 50

So the answer is 50

Akshay Jain
Dec 21, 2013

no. of sheeps (let) =x , no.of shepherds(let)=y
now, 4x+3y=300 and x+y=100 solving, x=50

Edsel Salariosa
Dec 20, 2013

let x the number of shepherds and let y the number of sheep . There are 300 legs in the field. Equate the first equation . 2x+4y=300 There are 100 heads in the field. Equate the 2nd equation. x+y=100. We have 2 equation and two unknown.Solve the equation by elimination . therefore x=50 shepherds and y=50 sheep

Prasun Biswas
Dec 20, 2013

Let us take the no. of sheeps as x. Since there are a total of 100 heads, so shepherds are (100-x).

Total no. of legs of the sheep = 4x and Total no. of legs of shepherds = 2(100-x)

According to the problem,

4 x + 2 ( 100 x ) = 300 4 x + 200 2 x = 300 2 x = 100 x = 50 4x+2(100-x)=300 \implies 4x+200-2x=300 \implies 2x=100 \implies x=50

So, no. of sheeps = x = 50 \boxed{50}

Michael Thornton
Dec 20, 2013

There are 300 legs in the field. Sheep have four legs and shepherds have two legs, so we must split these 300 legs in the ratio 2:4 - 2 + 4 = 6 2 + 4 = 6 300 / 6 = 50 300/6 = 50 50 times 2 = 100 and there are 300 legs in the field so we can split the legs into the ratio 100:200.

This means that there are 200 sheep legs in the field. As the ratio of sheep to legs is 1:4 (in other words, for every sheep there are four legs) we must divide 200 by 4 to get the number of sheep.

200 / 4 = 50 200 / 4 = \boxed{50}

Jezreel Almario
Dec 19, 2013

X=Sheep Y=Shepherd First Equation X+Y=100 -Total no. of heads Since Sheep have 4 legs and shepherds have 2 legs Second Equation 4X+2Y=300 -Total no. of legs

By substitution, X=50 and Y=50

Hùng Minh
Dec 19, 2013

Number of the heads: x + y = 100; Number of the legs: 2x + 4y = 100; <=> x = 50, y = 50

Ashtik Mahapatra
Dec 19, 2013

let there be x shepherds. Number of sheep=100-x A/Q => 2x + 4(100-x)=300 => 2x + 400 - 4x =300 => 2x = 100 => x=50

Jahir Shimanth
Dec 19, 2013

I think i have to fulfill 100 heads condition. so, for 200 hundred legs i got 50 sheep and for left 100 legs i got 50 shepherds. so there is total 50 sheep

Karthik Dayal
Dec 19, 2013

Its simple

  • no.of sheperds = X

    no.of sheeps = Y

  • we get 2 eqns.

    X + Y = 100

    2X + 4Y = 300

  • Solving we get 50 sheeps and 50 sheperds.

Nurul Alam Pavel
Dec 19, 2013

let, x be the number of ships,

and, y be the number of shepherds

we get two equations, x+y= 100 .........(1)

and 4x+2y= 300........................(2)

solving these equations we get, x= 50 , y = 50

therefore, number of ships is, 50

Sohail Khan
Dec 18, 2013

300 legs and 100 heads so assume there are 50 shephards each having 2 legs so, 300 legs - 100 legs = 200 legs. Now we are left with 50 heads and each sheep have 4 legs so, 50*4 legs=200 legs. So the shephards have 50 sheep.

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