MathCounts practice that meets you at your level.

Practice authentic past problems, open a hint when your thinking stalls, and watch each subject sharpen as you work.

Every problem is free. Always.

Algebra2026 Chapter Sprint #19

980

The first and twenty-first terms of an arithmetic progression are 26 and −4, respectively. How many positive terms does the progression have?

5 different subjectsA separate rating and focused practice for each one

Free for every studentThe full problem library, problem sets, and ratings cost $0

Hints from MathletesWritten by former Mathletes succeeding in competition math today

Build a problem setCustom

Choose a subject

AlgebraGeometryNumber Theory

Problems10

Problem sets

Build exactly the practice you need.

Choose a subject, length, and difficulty. Countdown builds a focused set from authentic past MathCounts problems, ready to start immediately.

The first and twenty-first terms of an arithmetic progression are 26 and −4, respectively. How many positive terms does the progression have?

Hint 1 of 5Use the formula for the n-th term of an arithmetic progression to relate the first term and the twenty-first term.

Guided practice

Get unstuck without giving away the problem.

Open one human-written hint at a time. Each hint moves your thinking forward while leaving the important work to you.

Friendboard

This week

1MMaya+361084

2YYou+281021

3AAlex+19994

Friendboard

Compete with your friends for Elo.

Add friends, compare ratings, and climb the Friendboard as you solve. Practice gets a little more exciting when someone you know is one spot ahead.

Our team

Built by students who wanted better practice.

We built Countdown to make serious MathCounts preparation accessible to every student, without a subscription, an expensive tutor, or a watered-down free tier.

Co-founder

Ethan Printz

Former Mathlete. Now a Competitive Programmer and Developer. USACO Gold, AIME Qualifier.

Co-founder

Bradley Yen

Former Mathlete. Now a Competitive Mathematician and Educator. USAJMO Honors, 2x MathCounts State Qualifier.