You could first turn the Values from String into Double like this:
(defn step1 [coll]
(map (fn [m]
(assoc m "Value" (Double/parseDouble (m "Value"))))
coll))
Next, you can use reduce to calculate the sum per Value:
(defn step2 [coll]
(reduce (fn [res m]
(let [k (m "Type")
v (m "Value")]
(assoc res k (+ v (get res k 0)))))
{}
coll))
This yields a map:
{"B" 6.982, "A" 37.599999999999994}
Finally, this map can be turned into the list that you want:
(defn step3 [m]
(map (fn [[k v]]
{"Type" k "Value" (format "%.3f" v)})
m))
The steps can be rolled into one function like this:
(defn der [coll]
(-> coll
step1
step2
step3))
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