youcubed: Polar Graph Art (9-12)
youcubed (Stanford University)

This activity allows students to explore ways to be creative by designing and making a pieces of art with polar graphs.

Illuminations: Balancing Act
Illuminations (National Council of Teachers of Mathematics)

Problems such as those in this activity help develop what students already know in preparation for writing equations and learning ways to solve for variables.

NRICH: Temperature
NRICH (University of Cambridge)

Is there a temperature at which Celsius and Fahrenheit readings are the same?

NRICH: Your Number Was...
NRICH (University of Cambridge)

Think of a number and follow my instructions. Tell me your answer, and I’ll tell you what you started with! Can you explain how I know?

NRICH: Fruity Totals
NRICH (University of Cambridge)

In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?

NRICH: Multiplication Mistake Age
NRICH (University of Cambridge)

Jane accidentally multiplied by 54 instead of 45, and her answer was 198 too big. What number did she multiply 54 by?

NRICH: Terminology
NRICH (University of Cambridge)

Given an equilateral triangle inside an isosceles triangle, can you find a relationship between the angles?

NRICH: CD Heaven
NRICH (University of Cambridge)

All CD Heaven stores were given the same number of a popular CD to sell for £24. In their two week sale each store reduces the price of the CD by 25% … How many CDs did the store sell at each price?

NRICH: Iff
NRICH (University of Cambridge)

Take a triangular number, multiply it by 8 and add 1. What is special about your answer? Can you prove it?

NRICH: Fair Shares?
NRICH (University of Cambridge)

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?

NRICH: How Old Am I?
NRICH (University of Cambridge)

In 15 years’ time my age will be the square of my age 15 years ago. Can you work out my age, and when I had other special birthdays?

NRICH: System Speak
NRICH (University of Cambridge)

Five equations… five unknowns… can you solve the system?