Answer:
1.05 hours
Explanation:
We need to use the least common multiple of 1.5 and 3.5 which is 10.5.
Thus we find how many lots each one will clear in 10.5 hours
Mart clears 1 lot in 1.5 hours
Number of Lots Time
1 ⇒ 1.5 hours
so in 10.5 hous:
Number of Lots Time
1 ⇒ 1.5 hours
x ⇒ 10.5 hours
the x is found by rule of three: multiply the cross quantities in the table (1 and 10.5) and dividing by the remaining amount (1.5):
x = 10.5*1/1.5
x = 7 lots
so Mark clears 7 lots in 10.5 hours.
His partner clears 1 lot in 3.5 hous:
Number of Lots Time
1 ⇒ 3.5 hours
so in 10.5 hous:
Number of Lots Time
1 ⇒ 3.5 hours
x ⇒ 10.5 hours
also by rule of three the x is:
x = 10.5*1/3.5
x = 3 lots
His partner clears 3 lots in the same 10.5 hours.
Thus, together:
Number of Lots Time
7+3 ⇒ 10.5 hours
simplifying:
Number of Lots Time
10 ⇒ 10.5 hours
and what we need to know is the time to clear one lot together:
Number of Lots Time
10 ⇒ 10.5 hours
1 ⇒ x
again, to find x we multiply cross quantities (10.5 by 1) and divide by the remaining amount (10):
x = 10.5*1/10
x = 1.05 hours
It will take them 1.05 hours to clear the lot