The doubles plus one are the facts in which one addend is larger than
the other by one. Examples 3+4=7, 6+7=13, 5+6=11, 3+2=5. Learning your
doubles plus one should involve knowing the doubles and mentally adding
the additional one. ubles are adding the same number together, as with 5+5=10.
With doubles +1, the numbers must be in beside each other in counting
order going up or down (ex: 4, 5, 6 and 9, 8, 7). I teach my first
graders to say the SMALLEST number, double it, then add one. So, 9+8
would be 8+8=16, +1=17. You must know your doubles facts before this
strategy is useful.
we know that in the triangle ABC ∠A+∠B+∠C=180° ∠C=180-(86+69)-----> ∠C=25° Applying the law of sines b/sin B=c/sin C------> b=c*sin B/sin C-----> b=82*sin 69/sin 25 b=181.14 ft