# GEOmetry(Special Coin Placement)

posted by .

Three coins are randomly placed into different positions on a 4×10 grid. The probability that no two coins are in the same row or column can be expressed as a/b where a and b are coprime positive integers. What is the sum of a+b?

• GEOmetry(Special Coin Placement) -

The total number of ways of choosing rows is 4C3, columns 10C3
Total number of ways of choosing 3 tiles among 40(4X10) is 40C3

## Similar Questions

1. ### Probabilities

A queen on an English chessboard is able to attack in the same row, column and diagonal. The probability that 2 randomly placed queens on an 8 by 8 chessboard will be able to attack each other can be expressed as a/b , where a and …
2. ### GEOMETRY

The squares of a 3×3 grid of unit squares are coloured randomly and independently so that each square gets one of 5 colours. Three points are then chosen uniformly at random from inside the grid. The probability that these points …
3. ### maths

Three coins are randomly placed into different positions on a 4×10 grid. The probability that no two coins are in the same row or column can be expressed as ab where a and b are coprime positive integers. What is the probability of …
4. ### Geometry

Two players each flip a fair coin. The probability that they get the same result can be expressed as a b where a and b are coprime positive integers. What is the value of a+b ?
5. ### mayh

Four players are playing a game involving choosing positions on a grid of size 3×8. Each player chooses a random position on the grid, then all players reveal their choices and a token is placed on each of the positions. The probability …
6. ### math

Four players are playing a game involving choosing positions on a grid of size 3×8. Each player chooses a random position on the grid, then all players reveal their choices and a token is placed on each of the positions. The probability …
7. ### Math (Probability)

Four players are playing a game involving choosing positions on a grid of size 3×8. Each player chooses a random position on the grid, then all players reveal their choices and a token is placed on each of the positions. The probability …
8. ### Math Help

Four players are playing a game involving choosing positions on a grid of size 3×8. Each player chooses a random position on the grid, then all players reveal their choices and a token is placed on each of the positions. The probability …
9. ### math

A queen on an English chessboard is able to attack in the same row, column and diagonal. The probability that 2 randomly placed queens on an 8 by 8 chessboard will be able to attack each other can be expressed as ab, where a and b …
10. ### maths

What is the maximum number of coins that can be placed on squares in an 8x8 chessboard such that each row, each column, and each long diagonal contains at most 4 coins?

More Similar Questions