emaths qn

• Maith

  25 Oct 08, 22:19

  H=4/5(220-n)

  make n the subject of this formula.

  H= 176 - 4/5n

  H-176 = -4/5n

  H - 176/- 4/5 = n

  correct? i dont have answer key so cannot check 

• deteq

  25 Oct 08, 22:22

  think its correct. u can change the fraction to - 5(H-76)/4 i think.

• iamapebble

  25 Oct 08, 22:25

  H = 4/5(220-n)
  H = 176 - 4/5n
  4/5n = 176 - H
  n = (176 - H) / (4/5)
  n = (176 - H)(5/4)
  n = 220 - (5/4)H

  I think you got the answer but remember your brackets are important. :)

• eagle

  26 Oct 08, 15:21

  Maith, got technique to check one. And very quick.

  Sub in values. For example,

  H=4/5(220-n)
  Sub n = 10,

  H = 0.8 * 210 = 168

   

  Then see iamapebble's answer
  n = 220 - (5/4)H

  Sub H = 168,
  n = 220 - 210
  n = 10

  Since you get back n = 10, it means it is correct.

  There are many such short techniques and strategies to do quick check for exams. Which is why I named my tuition as strategic tuition.... I like to focus on such quick check methods :D