Mary was working in a chemistry lab with a mixture of chemicals that was 90% water and weighed 20 po

A girl is twice as old as her brother and half as old as her father

hard · age 10+

Which triangle has a bigger area: 1

hard · age 10+

A certain number has three digits

hard · age 10+

What year comes next in this sequence: 1973 1979 1987 1993 1997 1999

hard · age 10+