With two people (A and B), there is one handshake
(A with B).

With three people (A, B, and C), there are three handshakes
(A with B and C; B with C).

With four people (A, B, C, and D), there are six handshakes
(A with B, C, and D; B with C and D; C with D).


In general, with n+1 people, the number of handshakes is the sum of the first n consecutive numbers: 1+2+3+ ... + n.


[size=18pt]in this case, the answer is '15'
[/size]

IF U R A GAMBLER - THIS FIGURE IS A SURE BET!



Don't think am a genius, am just like THOMAS EDISON! if u understand what i mean

The answer is simply 5.. There are five people at the party.. 5!=120 5x4x3x2x1=120

chloride6:
Mathematically, this is just permutation
X!/(X-R!R!) equals 120
Where
R is equal to 2
If x! Divides X-2!
We have x times x-1 divided by 2 equals 120
Which is x squared minus x equals 240
Which is a quadratic equation with a,b,c equal to 1, -1 and -240
Solving we have,
X equals 16 and -15
Since we can't have -15 people
Your answer is 16
Where is my gift OP?

I came rather late but you've gotten it already though it's not a permutation but a combination.

16

the number of people ar the number of nigerian problems. its uncountable!

Iamdagreatguy:
Weekend brain drill. The first to get the answer wins a prize:

At a birthday party, everyone shook hands with everybody else. There were 120 handshakes. How many people were at the party?

the answer is 121

60 persons
pls send my gift now ma number is 08030857359

16.
If there are n persons in the party, then the first person would have made (n-1) hand shakes and second would have made (n-2) hand shakes and so on. Thus the total number of hand shakes would amount to (n-1) + (n-2) + . . . + 1 = n(n-1)/2 = 120 from which n(n-1) = 240 = 16 x 15 and so n = 16.

there are only five people
see working:
simple permutation
let d no of people be n
n! (pronounced n factorial) = 120
⇨ n x (n-1) x (n-2) x (n-3) x ..∞ = 120
(ok let me not confuse you further...see detail advanced working gives n as 5)





Answer check:

5! = 5 x 4 x 3 x 2 x 1 = 120


(...Answer open to disprove sha..)









simple permutation

16. The answer can is the solution to the combinatorics equation below
nC2 = 120

the answer is 48....there are 48 persons in the party...

Let the number of people be n. Therefore, 1 person can only shake hands with (n-1) people. The rest (n-1) people will each shake hands with (n-1). Identical hand shakes will be repeated not times. Only one of the repeated handshake will be valid. Therefore, n(n-1) - (n-1)=120 Or n^2 - n - n+1 =120
Or n^2 = 121
n =square root of 121 = 11 There were eleven (11) people at the party

kenedy175:
5! (5 factorial) . They were definitely 5 people at the event

5×4×3×2×1=120

Do further maths in school, dem no go agree.

Even with ur further maths u failed woefully. the ans is 16.

2persons will shake once,
4persons will shake 4*3=12
10persons will shake 10*9=90
12persons will shale 11*12=132
...the question is NT accurate, except there is a person with one arm in d party.

olodos just full here
no wonder jamb don bring down cutoff marks

If there are 5 people, total number of handshakes will be 5*(5-1)
If there are 10 people, total number of handshakes will be 10*(10-1)...and so on...
In this case, the number of people present is the value of x in x*(x-1)=120
This yields a quadratic equation,
xsquared-x-120=0

Solve for x and get your answer. You'll have to deal with complex numbers though.

2persons will shake once,
4persons will shake 4*3=12
10persons will shake 10*9=90
11persons will shake 11*10=110
12persons will shale 11*12=132
...the question is NT accurate, except there is a person with one arm in d party.

Moneyyy:
All of you are Olodo, the answer is 30

Na u be d chief Olodo. Correct ans is 16. That's all.

Iamdagreatguy:
Weekend brain drill. The first to get the answer wins a prize:

At a birthday party, everyone shook hands with everybody else. There were 120 handshakes. How many people were at the party?

16 people.

mubarak001:
2persons will shake once,
4persons will shake 4*3=12
10persons will shake 10*9=90
12persons will shale 11*12=132
...the question is NT accurate, except there is a person with one arm in d party.

wrong! 10 person's will shake 45times, 16persons will shake 120 times

i think permutation will help get the answer but i dont know the formula. the question is puzzling

Situation001:
The answer is simply 5..
There are five people at the party..
5!=120
5x4x3x2x1=120

u sef think am nau

How can just 5 person's in a room shake 120times if they are to shake each other just once?

5persons will shake only 10times.

or draw 5 points on the ground and connect them. then count the number of connections


but if u draw 16points and connect each one to the other gives 120 connections

or use this formula
n (n-1 )
-------
2


it's actually a progression :
1 = 0 (add thes two numbs givs d next answer)
2 = 1 (add thes two numbs givs d next answer)
3 = 3 (add thes two numbs givs d next answer)
4 = 6
5 = 10
6 = 15
7 = 21
8 = 28
9 = 36
10 = 45
11 = 55
12 = 66
13 = 78
14 = 91
15 = 105
16 = 120

5!

5 pple

The answer is 16 people, 3:3, 4:6, 5:10, 6:15, 7:21, 8:28, 9:36, 10:45, 11:55, 12:66, 13:78, 14:91, 15:105 and finally 16:120

Iamdagreatguy

119 persons

The answer is 16 people, 3:3, 4:6, 5:10, 6:15, 7:21, 8:28, 9:36, 10:45, 11:55, 12:66, 13:78, 14:91, 15:105 and finally 16:120.....thanks

There were 16 people at the party.

Iamdagreatguy:
Weekend brain drill. The first to get the answer wins a prize:

At a birthday party, everyone shook hands with everybody else. There were 120 handshakes. How many people were at the party?

just 2 people. (everyone and everybody)

Let B = no of hand shakes.
Let A = no of people involved.

B = 120
A = ?

B = (A x (A-1))/2

120 = (A x (A-1))/2
240 = A² - A
A² - A - 240 = 0
(A + 15) (A - 16) = 0
A = -15, 16

A cannot be a negative value therefore, A = 16

The number of people involved in the handshakes = 16.

You can test my formula with smaller value of B like 1 to 10 handshakes.

basille:
700.

O.d.e

Hehehehehehehe! OP give question, go sleep when he neva give answer... Jobless people una doh ooo!