What is the value of n in the sequence 1, 3, 6, 10, 15, n ?

What is the circumference of a circle with a diameter 35 dm? (use $\pi$  = 3.14) 

The proper fractions  $\frac{n}{15}$  , $\frac{n}{16}$  , and  $\frac{n}{18}$  have the same numerator greater than 1 and are in simplest form. What is the least value of n?

A rectangle has an area of 300 square centimeters and a length of 25 centimeters. How many centimeters is its width?

Six pencils and 5 pens cost Php 136. If a pen costs twice as much as a pencil, how much will one pencil and one pen cost?

In the calendar shown, what month and date was the last Friday before August?