trip to Mexico and converting temp. and money.

I was trying to get my head wrapped around converting Temp. and money "pesos" and came up with several quick formulas. I know there are apps for this but wanted a quick way to convert especially pesos while walking around the market. Neither formula is exact but it is in the ball park.

Temp C. to F. C times 2 plus 30 = F. 15 degrees C X 2 = 30 + 30 = 60 degrees F. The real number is 59 degrees.

Pesos to USD. Pesos (drop the last 0) and divide by 2

500 pesos = 50 divided by 2 = $25 USD. The real number is $26.54

30 pecos = 3.0 divided by 2 = $1.50 the real number is $1.59.