There are **63** NRICH Mathematical resources connected to **Calculating with fractions**, you may find related items under Fractions, Decimals, Percentages, Ratio and Proportion.

What fraction of the black bar are the other bars? Have a go at this challenging task!

This task offers opportunities to subtract fractions using A4 paper.

Aisha's division and subtraction calculations both gave the same answer! Can you find some more examples?

Twisting and turning with ropes can be encoded mathematically using fractions. Can you find a way to get back to zero?

After training hard, these two children have improved their results. Can you work out the length or height of their first jumps?

Scientists often require solutions which are diluted to a particular concentration. In this problem, you can explore the mathematics of simple dilutions

How much of the square is coloured blue? How will the pattern continue?

The Egyptians expressed all fractions as the sum of different unit fractions. The Greedy Algorithm might provide us with an efficient way of doing this.

Can all unit fractions be written as the sum of two unit fractions?

It would be nice to have a strategy for disentangling any tangled ropes...

Take a look at the video and try to find a sequence of moves that will untangle the ropes.

Investigate this balance which is marked in halves. If you had a weight on the left-hand 7, where could you hang two weights on the right to make it balance?

Imagine you were given the chance to win some money... and imagine you had nothing to lose...

Ahmed is making rods using different numbers of cubes. Which rod is twice the length of his first rod?

A jigsaw where pieces only go together if the fractions are equivalent.

Can you see how to build a harmonic triangle? Can you work out the next two rows?

Andy had a big bag of marbles but unfortunately the bottom of it split and all the marbles spilled out. Use the information to find out how many there were in the bag originally.

A 750 ml bottle of concentrated orange squash is enough to make fifteen 250 ml glasses of diluted orange drink. How much water is needed to make 10 litres of this drink?

Ben passed a third of his counters to Jack, Jack passed a quarter of his counters to Emma and Emma passed a fifth of her counters to Ben. After this they all had the same number of counters.

Here is a picnic that Petros and Michael are going to share equally. Can you tell us what each of them will have?

Whenever a monkey has peaches, he always keeps a fraction of them each day, gives the rest away, and then eats one. How long could he make his peaches last for?

The Egyptians expressed all fractions as the sum of different unit fractions. Here is a chance to explore how they could have written different fractions.

The items in the shopping basket add and multiply to give the same amount. What could their prices be?

The discs for this game are kept in a flat square box with a square hole for each. Use the information to find out how many discs of each colour there are in the box.

Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?

A mother wants to share a sum of money by giving each of her children in turn a lump sum plus a fraction of the remainder. How can she do this in order to share the money out equally?

Explore the continued fraction: 2+3/(2+3/(2+3/2+...)) What do you notice when successive terms are taken? What happens to the terms if the fraction goes on indefinitely?

Can you use the given image to say something about the sum of an infinite series?

Can you compare these bars with each other and express their lengths as fractions of the black bar?

Can you find ways to make twenty-link chains from these smaller chains? This gives opportunities for different approaches.

Can you find combinations of strips of paper which equal the length of the black strip? If the length of the black is 1, how could you write the sum of the strips?

This challenge asks you to imagine a snake coiling on itself.

My recipe is for 12 cakes - how do I change it if I want to make a different number of cakes?

What does the empirical formula of this mixture of iron oxides tell you about its consituents?

Here is a chance to play a fractions version of the classic Countdown Game.

Which dilutions can you make using only 10ml pipettes?

Find out why these matrices are magic. Can you work out how they were made? Can you make your own Magic Matrix?

Can you work out the height of Baby Bear's chair and whose bed is whose if all the things the three bears have are in the same proportions?

The harmonic triangle is built from fractions with unit numerators using a rule very similar to Pascal's triangle.

Use the fraction wall to compare the size of these fractions - you'll be amazed how it helps!

Find the maximum value of 1/p + 1/q + 1/r where this sum is less than 1 and p, q, and r are positive integers.

Can you find the value of this function involving algebraic fractions for x=2000?

Anne completes a circuit around a circular track in 40 seconds. Brenda runs in the opposite direction and meets Anne every 15 seconds. How long does it take Brenda to run around the track?

Can you predict, without drawing, what the perimeter of the next shape in this pattern will be if we continue drawing them in the same way?

Sometime during every hour the minute hand lies directly above the hour hand. At what time between 4 and 5 o'clock does this happen?

On Saturday, Asha and Kishan's grandad took them to a Theme Park. Use the information to work out how long were they in the theme park.

One quarter of these coins are heads but when I turn over two coins, one third are heads. How many coins are there?