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Answer:
The value is 
Step-by-step explanation:
Generally the productivity rate is mathematically represented as

Here K is the ha the farmer could harvest in an hour and Z is a typical yield of corn in kg/ha
Now considering 1970
The productivity rate is

=>
Now considering 1940
The productivity rate is given as
Generally the productivity ratio is mathematically ration is mathematically represented as

=> 
=> 
Answer:
1/2
Step-by-step explanation:
Answer :
the answer is -4/5 or -0.8
step-by-step explanation:
1-9/7+3 = -8/10
now simplify that,
-8/2 = -4
10/2 = 5
so we have -4/5 0r -0.8