geometry

This might help

https://web2.0calc.com/questions/rhombus-nbsp-abcd-nbsp-has-perimeter-148-nbsp-and-one-of-its-diagonals-has-length-nbsp-24-nbsp-what-is-the-area-of-abcd

1/  All sides of the rhombus are equal.

2/  The opposite sides of a rhombus are parallel.

3/  Opposite angles of a rhombus are equal.

4/  In a rhombus, diagonals bisect each other at right angles.

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Side  a = 160 / 4 = 40

 

1/2 of the diagonal is  30 / 2 = 15

 

sqrt(40² - 15²) =  √1375

 

A = 2( 15 * √1375 )