"Front-end strategy" is a method for estimating an answer to a calculation problem by focusing on the "front-end" or "left-most" digits of a number.

Its strongest application is for addition.

You buy a hamburger for $4.79, a drink for $1.26 and an ice-cream cone for $0.95. Will a five dollar bill cover the cost?

Total the front-end (dollar) amounts: $4 + $1 = $5.

A five dollar bill will not cover the cost because the front-end estimate, which is always an underestimate, is $5.