I don't quite understand the ten strategy, or what EXACTLY you're asking. But, what you can do is when you add a one digit number plus a nine, just change the nine to a ten and subtract one. It is very easy. So, 7+10 equals 17, subtract one and you get 16 which is 7+9. It is always one less than anything plus 10.
Answer:
x=4.34 seconds
Step-by-step explanation:
-16x^2+70x-2=0
x=4.34
We have 1.2 × 10^(-4) x 6.25 × 10^(-5 ) = 7,5 x 10^(-9) = 75 x 10^(-10) square kilometers.
