5. Five marks example problems III

1. Find the sum of all natural numbers between \(300\) and \(600\) that are divisible by \(7\).

 

Answer:

 

Sum \(=\)

 

 

2. A mosaic is designed in the shape of an equilateral triangle, \(12 \ ft\) on each side. Each tile in the
mosaic is in the shape of an equilateral triangle of \(12\) inch side. The tiles are alternately coloured, as shown in the figure. Find the number of tiles of each colour and the total number of tiles in the mosaic.

 

 

Answer:

 

Number of white tiles \(=\)

 

Number of blue tiles \(=\)

 

Total number of tiles \(=\)

 

 

3. The houses on a street are numbered from \(1\) to \(49\). Senthil’s house is numbered such that the sum of the numbers of the houses prior to Senthil’s house is equal to the sum of the numbers of the houses following Senthil’s house. Find Senthil’s house number?

 

Answer:

 

Senthil’s house number \(=\)