You may also like

problem icon

Old Nuts

In turn 4 people throw away three nuts from a pile and hide a quarter of the remainder finally leaving a multiple of 4 nuts. How many nuts were at the start?

problem icon

N000ughty Thoughts

How many noughts are at the end of these giant numbers?

problem icon

Mod 3

Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3.

Sixational

Age 14 to 18 Challenge Level:

The $n$th term of a sequence is given by the formula

$n^3 + 11n$.

Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million.

Prove that all terms of the sequence are divisible by $6$.


The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.
Copyright © 1997 - 2020. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project.