Ratio and proportion

There are 112 NRICH Mathematical resources connected to Ratio and proportion
Timber!
problem

Timber!

Age
7 to 11
Challenge level
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How can the school caretaker be sure that the tree would miss the school buildings if it fell?
Cherry Buns
problem

Cherry Buns

Age
7 to 11
Challenge level
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Sam's grandmother has an old recipe for cherry buns. She has enough mixture to put 45 grams in each of 12 paper cake cases. What was the weight of one egg?
Hello Again
problem

Hello Again

Age
11 to 14
Challenge level
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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?
ArRh!
problem

ArRh!

Age
14 to 16
Challenge level
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Triangle ABC is equilateral. D, the midpoint of BC, is the centre of the semi-circle whose radius is R which touches AB and AC, as well as a smaller circle with radius r which also touches AB and AC. What is the value of r/R?
A Shade Crossed
problem

A Shade Crossed

Age
14 to 16
Challenge level
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Find the area of the shaded region created by the two overlapping triangles in terms of a and b?
Halving the Triangle
problem

Halving the Triangle

Age
16 to 18
Challenge level
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Draw any triangle PQR. Find points A, B and C, one on each side of the triangle, such that the area of triangle ABC is a given fraction of the area of triangle PQR.
Conical Bottle
problem

Conical Bottle

Age
14 to 16
Challenge level
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A right circular cone is filled with liquid to a depth of half its vertical height. The cone is inverted. How high up the vertical height of the cone will the liquid rise?
Chord
problem

Chord

Age
16 to 18
Challenge level
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Equal touching circles have centres on a line. From a point of this line on a circle, a tangent is drawn to the farthest circle. Find the lengths of chords where the line cuts the other circles.
Golden Ratio
problem

Golden Ratio

Age
16 to 18
Challenge level
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Solve an equation involving the Golden Ratio phi where the unknown occurs as a power of phi.
Rati-o
problem

Rati-o

Age
11 to 14
Challenge level
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Points P, Q, R and S each divide the sides AB, BC, CD and DA respectively in the ratio of 2 : 1. Join the points. What is the area of the parallelogram PQRS in relation to the original rectangle?