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Count how many weekdays (Mon–Fri) fall between two dates, plus the number of business days once Japanese public holidays are removed.

Simulate your Texas Hold'em win, tie and loss rates from your hole cards, the community cards and the number of opponents using a Monte Carlo method.

From your age, your parent's age, and how often you meet, this tool estimates how many more times you'll see them and the odds, based on life-table survival rates.

From your age and sex, estimate how many more times you will see cherry blossoms, based on Japanese life tables. Also shows your odds of being alive in 5 or 10 years.

Solve the classic cranes-and-turtles word problem: find how many of each from the total heads and total legs, with a step-by-step solution and a check.

Solve the classic surplus and shortage word problem: from giving a items each with X left over and b items each falling Y short, find the number of people and the total.

If a job takes P people D days, find how many people are needed to finish it in d days. Shows the total work and step-by-step solution.

Find how many days it takes p workers to finish a job that P workers do in D days. Shows the total work and a step-by-step solution.

If A finishes a job alone in a days and B in b days, find how many days they need working together. Shows the daily work rate and the full solving steps.

Find how many trees fit along a path from its length and the spacing between trees. Handles four classic word problem cases: both ends, one end, neither end, and a circular path, with the number of gaps and step by step reasoning.

A parent is now a certain age and their child another. Find in how many years the parent will be exactly a chosen multiple of the child age. This classic word problem uses the constant age difference and shows the solving steps.

Solve the classic age word problem: from the age difference, a number of years later, and a multiple, find the current ages of parent and child.

Find the concentration when two salt solutions are mixed. A classic word problem solver that works from total salt and total weight, with steps.

Find the concentration after adding water to a salt solution, or the amount of water needed to reach a target concentration, with step-by-step working.

Solve classic salt-water word problems about making a solution stronger, with clear steps.

Enter the sum and difference of two numbers and instantly find the larger and smaller number. Includes a bar diagram, step-by-step solution, and a check.

Find downstream and upstream speeds from a boat speed in still water and the current speed, or work backward from downstream and upstream speeds, and get travel time for a given distance.

Find when two people moving toward each other from a given distance apart will meet, plus each person's travel distance and the meeting point.

Find the time to catch up and the distance to the meeting point from the leader speed, chaser speed, and head start distance or time gap.

Find the angle between the hour and minute hands at any time, or the time when the hands overlap, form a straight line, or make a right angle.

Calculate the probability of rolling a given total with several dice. Shows the exact probability of a target sum, the at-least and at-most probabilities, expected value, variance, and a bar chart of the distribution.

Compute the expected number of draws needed to collect all n distinct items using the harmonic number.

Calculate the probability that two people in a group of n share a birthday. Explore the surprising birthday paradox with a probability curve.

Find the chance that someone among n people shares your exact birthday. Using 1 minus (364/365) to the power n, see the match chance, the no-match chance, and how many people pass 50 percent.

Test whether a die is fair with a chi-square goodness-of-fit test. Enter the count for each face to get the chi-square statistic, degrees of freedom, p-value, and a verdict at the 5% level.

Find the standard error and 95% confidence interval margin from a sample size and a proportion such as a TV rating.

Find the chance that one round of rock paper scissors among n players ends without a tie.

Enter how often your opponent throws rock, scissors, and paper to find your best move plus win, draw, and loss probabilities, with an optional simulation.

Enter score, course rating, and slope rating for each round to compute differentials and your handicap index automatically.

Estimate the chance of being in a fatal aviation accident over a lifetime from the per-flight accident rate and your number of flights, with a Monte Carlo simulation and histogram.

Generate uniform random integers within a range. Choose the count and whether duplicates are allowed.

Generate random numbers that follow a normal distribution from a mean and standard deviation, with a histogram and sample statistics.

Generate random numbers from a lognormal distribution. Enter the parameters mu and sigma and a count, then click to produce a sample list, histogram, and sample mean and median.

Generate random numbers from a gamma distribution with shape k and scale theta. Shows a sample list, histogram, sample mean and sample variance.

Generate random numbers from a chi-square distribution by setting degrees of freedom k and a sample size. Shows the sample mean, variance, and a histogram.

Generate random numbers from a Student t-distribution with a chosen degrees of freedom. Shows the list, a histogram, and sample mean and standard deviation.

Roll n dice with m faces as many times as you like. See each roll, its total, the distribution of totals, and the average.

Three basic percentage calculations in one: what percent A is of B, a given percent of a number, and the whole from a part and its percentage. Enter two numbers to instantly get the percent or amount, with your choice of decimal places and rounding.

Enter a starting (old) value and an ending (new) value to instantly get the percent change, the year-over-year ratio, and the absolute difference. Great for sales, prices, population, and traffic growth.